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ENB 449

Clive

THE SUN IS A SOLAR-TYPE STAR
American Association for the Advancement of Science

A new study claims that the Sun is a solar-type star, -- resolving an
ongoing controversy about whether the star at the centre of our Solar
System exhibits the same cyclic behaviour as other 'nearby' solar-type
stars. The results also advance scientists' understanding of how stars
generate their magnetic fields. The Sun's activity -- including changes
in the number of sunspots, levels of radiation and ejection of material --
varies on an eleven-year cycle, driven by changes in its magnetic field.
Understanding that cycle is one of the biggest outstanding problems in
solar physics, in part because it does not appear to match magnetic
cycles observed in other solar-type stars -- leading some astronomers
to suggest that the Sun is fundamentally different. By carrying out
a series of simulations of stellar magnetic fields, researchers show
that the Sun's magnetic cycle depends on its rotation rate and
luminosity. The relationship can be expressed in terms of the
so-called Rossby number. Comparing the results of their simulations
with available observations of cyclic activity in a sample of nearby
solar-type stars, the team further finds that the cycle periods of the
Sun and other solar-type stars all follow the same relationship with
the Rossby number.


NEW EVIDENCE FOR PLANET 9
SINC

Scientists continue to argue about the existence of a ninth planet
in the Solar System. At the beginning of 2016, researchers from the
California Institute of Technology announced that they had evidence of
the existence of such an object, located at an average distance of 700
astronomical units (700 times the Earth-Sun separation) and with a
mass ten times that of the Earth. Their calculations were motivated by
the peculiar distribution of the orbits found for the trans-Neptunian
objects (TNO) of the Kuiper belt, which apparently revealed the
presence of a Planet Nine or X in the confines of the Solar System.
However, scientists from the Canadian-French-Hawaiian project OSSOS
detected biasses in their own observations of the orbits of the TNOs,
which had been systematically directed towards the same regions of the
sky, and considered that other groups, including the Caltech group,
may be experiencing the same issues. According to those scientists,
it is not necessary to propose the existence of a massive perturber
(a Planet Nine) to explain the observations, as they are compatible
with a random distribution of orbits. Now, however, two astronomers
from the Complutense University of Madrid have applied a new tech-
nique, less exposed to observational bias, to study a special type of
trans-Neptunian objects -- the extreme ones (ETNOs, located at average
distances greater than 150 AU and that never cross Neptune's orbit).
For the first time, the distances from their nodes to the Sun have
been analysed, and the results once again indicate that there is a
planet beyond Pluto. The nodes are the two points at which the orbit
of an ETNO, or any other celestial body, crosses the plane of the
Solar System. Those are the precise points where the probability of
interacting with other objects is the largest, and therefore, at those
points the ETNOs may experience drastic changes in their orbits or
even a collision.

If there is nothing to perturb them, the nodes of the extreme trans-
Neptunian objects should be uniformly distributed, as there is nothing
for them to avoid, but if there are one or more perturbers, two
situations may arise. One possibility is that the ETNOs are stable,
and in that case they would tend to have their nodes away from the
path of possible perturbers, but if they are unstable they would
behave as the comets that interact with Jupiter do, that is tending to
have one of the nodes close to the orbit of the hypothetical perturber.
Using calculations and data mining, the Spanish astronomers have found
that the nodes of the 28 ETNOs analysed (and the 24 extreme Centaurs
with average distances from the Sun of more than 150 AU) are clustered
in certain ranges of distances from the Sun; furthermore, they have
found a correlation, where none should exist, between the positions of
the nodes and the inclination, one of the parameters which defines the
orientation of the orbits of the objects in space. Assuming that the
ETNOs are dynamically similar to the comets that interact with Jupiter,
the team interprets those results as signs of the presence of a planet
that is actively interacting with them in a range of distances from
300 to 400 AU. Astronomers believe that what they are seeing here
cannot be attributed to observational bias. Until now, studies that
challenged the existence of Planet Nine using the data available for
trans-Neptunian objects argued that there had been systematic errors
linked to the orientations of the orbits (defined by three angles),
owing to the way in which the observations had been made. Neverthe-
less, the nodal distances mainly depend on the size and shape of the
orbit, parameters which are relatively free from observational bias.

The authors note that their study supports the existence of a planet-
ary object within the range of parameters considered both in the
Planet-Nine hypothesis of Mike Brown and by Konstantin Batygin from
Caltech. The hypothetical Planet Nine suggested in this study has
nothing to do with another possible planet or planetoid situated much
closer to us, and hinted at by other recent findings. Also, applying
data mining to the orbits of the TNOs of the Kuiper Belt, astronomers
from the University of Arizona have found that the plane on which
these objects orbit the Sun is slightly warped, a fact that could be
explained if there is a perturber of the size of Mars at 60 AU from
the Sun. Given the current definition of planet, that other putative
object might not be a true planet, even if it has a size similar to
that of the Earth, as it could be surrounded by huge asteroids or
dwarf planets. In any case, scientists are convinced that the work
has found solid evidence of the presence of a massive body beyond the
so-called Kuiper Cliff, the furthest point of the trans-Neptunian
belt, at some 50 AU from the Sun.


LARGE,DISTANT COMETS MORE COMMON THAN THOUGHT
NASA

Comets that take more than 200 years to make one revolution around the
Sun are notoriously difficult to study. Because they spend most of
their time far from our part of the Solar System, many 'long-period
comets' will never approach the Sun in any particular person's
lifetime. In fact, those that travel inward from the Oort Cloud --
a group of icy bodies beginning roughly 5000 AU away from the Sun --
can have periods of thousands or even millions of years. NASA's WISE
space-craft, scanning the entire sky at infrared wavelengths, has
delivered new insights about those distant wanderers. Scientists
found that there are about seven times more long-period comets
measuring at least 1 kilometre across than had been predicted
previously. They also found that long-period comets are on average up
to twice as large as 'Jupiter-family comets', whose orbits are shaped
by Jupiter's gravity and have periods less than 20 years. Researchers
also observed that in eight months, three to five times as many long-
period comets passed by the Sun as had been predicted. The Oort Cloud
is too distant to be seen by current telescopes, but is thought to be
a spherical distribution of small icy bodies at the outermost edge of
the Solar System. The density of comets within it is low, so the odds
of comets colliding within it are rare. Long-period comets that WISE
observed probably got kicked out of the Oort Cloud millions of years
ago. The observations were carried out during the spacecraft's
primary mission before it was renamed NEOWISE and reactivated to
target near-Earth objects (NEOs). Astronomers already had broader
estimates of how many long-period and Jupiter-family comets exist in
the Solar System, but had no good way of measuring the sizes of long-
period comets. That is because a comet has a 'coma', a cloud of gas
and dust that appears hazy in images and obscures the cometary
nucleus. But by using the WISE data showing the infrared glow of the
coma, scientists were able to subtract the coma from the overall
comet and estimate the nucleus sizes of the comets. The data came
from 2010 WISE observations of 95 Jupiter family comets and 56 long-
period comets.

The results reinforce the idea that comets that pass by the Sun more
often tend to be smaller than those spending much more time away from
the Sun. That is because Jupiter-family comets get more heat exposure,
which causes volatile substances like water to sublimate and drag away
other material from the comet's surface as well. The existence of so
many more long-period comets than predicted suggests that more of them
are likely to have impacted planets, delivering icy materials from the
outer reaches of the Solar System. Researchers also found clustering
in the orbits of the long-period comets that they studied, suggesting
that there could have been larger bodies that broke apart to form
those groups. The results will be important for assessing the likeli-
hood of comets impacting planets, including the Earth. Comets travel
much faster than asteroids, and some of them are very big. Studies
such as the one reported here may help us to define what kind of
hazard long-period comets may pose.


SMALLEST-EVER STAR DISCOVERED
University of Cambridge

The smallest star yet measured has been discovered by a team of
astronomers led from the University of Cambridge. With a size just
slightly larger than Saturn, the gravity at its surface is about 300
times stronger than gravity on the Earth. The star is probably about
as small as stars can possibly be, as it has just enough mass to
enable the fusion of hydrogen nuclei into helium. If it were any
smaller, the pressure at the centre of the star would no longer be
sufficient to enable that process to take place. Hydrogen fusion is
also what powers the Sun. Such very small and dim stars are also the
best possible candidates for detecting Earth-sized planets which can
have liquid water on their surfaces, such as TRAPPIST-1, an ultra-cool
dwarf surrounded by seven temperate Earth-sized worlds. The newly-
measured star, called EBLM J0555-57Ab, is located about 600 light
years away. It is part of a binary system, and was identified as it
passed in front of its much larger companion, a method which usually
detects planets, not stars. EBLM J0555-57Ab was identified by WASP, a
planet-finding experiment run by the Universities of Keele, Warwick,
Leicester and St Andrews.

The parent star became dimmer in a periodic fashion, the signature of
an orbiting object. Thanks to that special configuration, researchers
can measure accurately the mass and size of any orbiting companions,
in this case a small star. The mass of EBLM J0555-57Ab was established
by the Doppler method, using data from the CORALIE spectrometer. The
newly-measured star has a mass comparable to the current estimate for
TRAPPIST-1, but has a radius that is nearly 30% smaller. The smallest
stars provide optimal conditions for the discovery of Earth-like
planets, and for the remote exploration of their atmospheres. However,
before we can study planets, we need to understand their stars.
Although they are the most numerous stars in the Universe, stars with
sizes and masses less than 20% that of the Sun are poorly understood,
since they are difficult to detect owing to their small size and low
brightness. The EBLM project, which identified the star in this
study, aims to plug that gap in knowledge.


COSMIC 'DUST FACTORY' REVEALS CLUES TO HOW STARS ARE BORN
RAS

Researchers at Cardiff University have discovered a rich inventory of
molecules at the centre of an exploded star for the very first time.
Two previously undetected molecules, formylium (HCO+) and sulphur
monoxide (SO), were found in the cooling aftermath of Supernova 1987A,
located 163,000 light-years away in the Large Magellanic Cloud - a
'nearby' neighbour of our own Milky Way galaxy. The newly identified
molecules were accompanied by previously detected compounds such as
carbon monoxide (CO) and silicon oxide (SiO). The researchers estimate
that about 1 in 1000 silicon atoms from the exploded star can be found
in SiO molecules and only a few out of every million carbon atoms are
in HCO+ molecules. It was previously thought that the massive
explosions of supernovae would completely destroy any molecules and
dust that may already have been present. However, the detection of
those unexpected molecules suggests that the explosive death of stars
could lead to clouds of molecules and dust at extremely cold tempera-
tures -- conditions similar to those seen in stellar nurseries where
stars are born. The results show that as the leftover gas from a
supernova begins to cool down to below 200°C, the many heavy elements
that are synthesized can begin to harbour rich molecules, creating a
dust factory. What is most surprising is that this factory of rich
molecules is usually found in conditions where stars are born. The
deaths of massive stars may therefore lead to the birth of a new
generation.

The team used the Atacama Large Millimeter/submillimeter Array (ALMA)
to observe the heart of Supernova 1987A in remarkably fine detail.
Astronomers have been studying SN 1987A since it was first discovered
30 years ago, but have found it difficult to analyze the supernova's
innermost core. ALMA's ability to observe at millimetre wavelengths
-- a region of the electromagnetic spectrum between infrared light and
radio waves -- made it possible to see through the intervening dust
and gas, and study the abundance and location of the newly formed mol-
ecules. The ALMA observations of molecules such as silicon monoxide
in SN 1987A have enabled isotopic abundance ratios to be measured for
the first time in supernova material, allowing comparisons to be made
with models for the explosive nuclear reactions that take place in
such supernovae. In an accompanying paper, a second research team
has used ALMA's data to create the first 3D model of SN 1987A,
offering important insights into the original star itself and the way
supernovae create the basic building blocks of planets. It is well
understood that massive stars, those more than 10 times the mass of
the Sun, end their existence in spectacular fashion. When such a star
runs out of fuel, there is no longer enough heat and energy to sustain
the star against the force of its own gravity. The outer reaches of
the star, once held up by the power of nuclear fusion, then come
crashing down on the core with tremendous force. The rebound from
that collapse triggers an explosion that blasts material into space.
Building on its current findings, the team hopes to use ALMA to find
out exactly how abundant the molecules of HCO+ and SO are, and to see
if there are within the supernova any other molecules that have yet to
be detected.


HIGH-ENERGY TRAP IN CENTRE OF MILKY WAY
NASA/Goddard Space Flight Center

A combined analysis of data from NASA's Fermi Gamma-ray Space
Telescope and the High-Energy Stereoscopic System (HESS), a
ground-based observatory in Namibia, suggests that the centre of our
Milky Way contains a 'trap' that concentrates some of the highest-
energy cosmic rays, among the fastest particles in the galaxy. Cosmic
rays are high-energy particles moving through space at almost the
speed of light. About 90% of them are protons, with electrons and the
nuclei of various atoms making up the rest. In their journey across
the Galaxy, those electrically charged particles are affected by
magnetic fields, which alter their paths and make it impossible to
know where they originated. But astronomers can learn about cosmic
rays when they interact with matter and emit gamma rays, the highest-
energy form of light. In 2016 March, scientists with the HESS
Collaboration reported gamma-ray evidence of the extreme activity in
the Galactic Centre. The team found a diffuse glow of gamma rays
reaching nearly 50 trillion electron volts (TeV). That's some 50
times greater than the gamma-ray energies observed by Fermi's Large
Area Telescope (LAT). To put those numbers in perspective, the energy
of visible light ranges from about 2 to 3 electron volts.

The Fermi spacecraft detects gamma rays when they enter the LAT. On
the ground, HESS detects the emission when the atmosphere absorbs
gamma rays, which triggers a cascade of particles resulting in a flash
of blue light. In a new analysis, an international team of scientists
combined low-energy LAT data with high-energy HESS observations.
The result was a continuous gamma-ray spectrum describing the Galactic
Centre emission across a thousandfold span of energy. Once the bright
point sources were subtracted, good agreement was found between the
LAT and HESS data, which was somewhat surprising owing to the
different energy windows and observing techniques used. The agreement
indicates that the same population of cosmic rays -- mostly protons --
found throughout the rest of the Galaxy is responsible for gamma rays
observed from the Galactic Centre. But the highest-energy share of
those particles, those reaching 1,000 TeV, move through the region
less efficiently than they do everywhere else in the Galaxy. That
results in a gamma-ray glow extending to the highest energies HESS
observed. The most energetic cosmic rays spend more time in the
central part of the Galaxy than previously thought, so they make a
stronger impression in gamma rays. That effect is not included in
conventional models of how cosmic rays move through the Galaxy.
But the researchers show that simulations incorporating that change
display even better agreement with Fermi data. The same breakneck
particle collisions responsible for producing the gamma rays should
also produce neutrinos, the fastest, lightest and least-understood
fundamental particles. Neutrinos travel straight to us from their
sources because they barely interact with other matter and because
they carry no electrical charge, so magnetic fields don't sway them.
Experiments like IceCube in Antarctica are detecting high-energy
neutrinos from beyond the Solar System, but pinpointing their sources
is much more difficult. The findings from Fermi and HESS suggest
that the Galactic Centre could be detected as a strong neutrino source
in the near future.


ONE OF BRIGHTEST GALAXIES EVER DISCOVERED
Instituto de Astrofisica de Canarias (IAC)

According to Einstein's theory of General Relativity, when a ray of
light passes close to a very massive object the gravity of the object
attracts the photons and deviates them from their initial path. That
phenomenon, known as gravitational lensing, is comparable to that
produced by lenses on light rays, and acts as a sort of magnifier,
changing the size and intensity of the apparent image of the original
object. Taking advantage of that effect, a team of scientists has
discovered a very distant galaxy, some 10 billion light-years away,
about a thousand times brighter than the Milky Way. It is the
brightest of the sub-millimetre galaxies, so called because of their
very strong emission in the far infrared. To measure it they used the
Gran Telescopio Canarias (GTC) on La Palma. Thanks to the
gravitational lens produced by a cluster of galaxies between ourselves
and the source, which acts as if it were a telescope, the galaxy appears
11 times bigger and brighter than it really is, and appears as several
images on an arc centred on the densest part of the cluster, which is
known as an 'Einstein Ring'. An advantage of that kind of
amplification is that it does not distort the spectral properties of the light,
which can be studied for even very distant objects as if they were much
nearer.

The galaxy is notable for having a high rate of star formation. It is
forming stars at a rate of 1000 solar masses per year, compared to the
Milky Way which is forming stars at a rate of some two a solar masses
a year. Such objects harbour the most powerful star-forming regions
known in the Universe. The next step will be to study their molecular
content. The fact that the galaxy is so bright, its light is gravi-
tationally amplifed, and has multiple images, allows us to look into
its internal properties, which would otherwise not be possible with
such distant galaxies. In the future we will be able to make more
detailed studies of its star formation using interferometers such as
the Northern Extended Millimeter Array (NOEMA/IRAM), in France, and
the Atacama Large Millimeter Array (ALMA), in Chile.


SUPERLUMINOUS SUPERNOVAE
RAS

The death of a massive star in a distant galaxy 10 billion years ago
created a rare superluminous supernova that astronomers say is one of
the most distant ever discovered. The brilliant explosion, more than
three times as bright as the 100 billion stars of our Milky Way
galaxy combined, occurred about 3.5 billion years after the Big Bang
when the rate of star formation in the Universe reached its peak.
Superluminous supernovae are 10 to 100 times brighter than the typical
supernova resulting from the collapse of a massive star. But astron-
omers still don't know exactly what kinds of stars give rise to their
extreme luminosity or what physical processes are involved. The
supernova known as DES15E2mlf is unusual even among the small number
of superluminous supernovae astronomers have detected so far. It was
initially detected in 2015 November by the Dark Energy Survey (DES)
collaboration using the Blanco 4-metre telescope at the Cerro Tololo
Inter-American Observatory in Chile. Follow-up observations to
measure the distance and obtain detailed spectra of the supernova were
conducted with the Gemini Multi-Object Spectrograph on the 8-metre
Gemini South telescope. The new observations may provide clues to the
nature of stars and galaxies during peak star formation. Supernovae
are important in the evolution of galaxies because their explosions
enrich the interstellar gas, from which new stars form with elements
heavier than helium (which astronomers call "metals"). Previous
observations of superluminous supernovae found they typically reside
in low-mass or dwarf galaxies, which tend to be less enriched in
metals than more massive galaxies. The host galaxy of DES15E2mlf,
however, is a fairly massive, normal-looking galaxy.

The current idea is that a low-metal environment is important in
creating superluminous supernovae, and that is why they tend to occur
in low-mass galaxies, but DES15E2mlf is in a relatively massive galaxy
compared to the typical host galaxy for superluminous supernovae.
Stars with fewer heavy elements retain a larger fraction of their
mass when they die, which may cause a bigger explosion when the star
exhausts its fuel supply and collapses. Metallicity affects the life
of a star and how it dies, so finding this superluminous supernova in
a higher-mass galaxy goes counter to current thinking. But we are
looking so far back in time, that galaxy would have had less time to
create metals, so it may be that at those earlier times in the
Universe's history, even high-mass galaxies had low enough metal
content to create such extraordinary stellar explosions. At some
point, the Milky Way also had those conditions and might also have
produced a lot of such explosions. Although many puzzles remain, the
ability to observe the unusual supernovae at such great distances
provides valuable information about the most massive stars and about
an important period in the evolution of galaxies. The Dark Energy
Survey has discovered a number of superluminous supernovae and
continues to see more distant cosmic explosions, revealing how stars
exploded during the strongest period of star formation.


AUSTRALIA ENTERS INTO PARTNERSHIP WITH ESO
ESO

An arrangement has been signed to begin a ten-year strategic partner-
ship between ESO and Australia. The partnership will further streng-
then ESO's programme, both scientifically and technically, and will
give Australian astronomers and industry access to the La Silla
Paranal Observatory. It may also be the first step towards Australia
becoming an ESO Member State. It means that Australia will contribute
financially to ESO for ten years, with the potential of then obtaining
full membership. The partnership will allow Australian astronomers to
participate in all activities relating to ESO's La Silla Paranal
Observatory facilities -- specifically, the Very Large Telescope, the
Very Large Telescope Interferometer, VISTA, VST, the ESO 3.6-metre
telescope, and the New Technology Telescope. The partnership will
also open opportunities for Australian scientists and industry to
collaborate with ESO Member State institutions on upcoming instruments
at those observatories.

ENB 448

Clive

CALM LAKES ON TITAN
University of Texas at Austin

The lakes of liquid methane on Saturn's moon, Titan, might be good for
paddling but not for surfing (for people who did not mind the cold --
methane boils at -161 C at normal terrestrial atmospheric pressure --
and whose feet were not harmed by liquid methane)! New research has
found that most waves on Titan's lakes reach only about 1 centimetre
high, a finding that indicates a serene environment that could be good
news for future probes sent to the surface of that moon. Titan is the
largest moon of Saturn and one of the locations in the Solar System
that is thought to possess the ingredients for life. In photos taken
by the Cassini orbiter, it appears as a smooth brown orb because of
its thick atmosphere clouded with gaseous nitrogen and hydrocarbons.
However, radar images from the same probe show that it has a surface
crust made of water ice and drenched in liquid hydrocarbons. Methane
and ethane fall from the sky on Titan as rain, fill deep lakes that
dot the surface, and are possibly spewed into the air by icy volcanoes
called cryovolcanoes. The atmosphere of Titan is very complex, and it
does synthesize complex organic molecules. It may act as a laboratory
of sorts, where basic molecules can be transformed into more complex
molecules that could eventually lead to life. On top of that, it is
also thought to have an ocean of liquid water beneath its icy crust.

Scientists developed a technique for measuring surface roughness in
minute detail from radar data. Called radar statistical reconnaiss-
ance, the technique has been used to measure the snow density and
surface roughness in Antarctica and the Arctic, and to assist the
landing-site selection of NASA's Mars lander InSight, which is
scheduled to be launched next year. Researchers at the Jet Propulsion
Laboratory suggested using the technique to measure Titan's waves.
The research refers to the three largest lakes in Titan's northern
hemisphere: Kraken Mare, Ligeia Mare and Punga Mare. Kraken Mare, the
largest of the three, is estimated to be larger than the Caspian Sea.
By analyzing radar data collected by Cassini during Titan's early-
summer season, the team found that waves on the lakes are diminutive,
reaching only about 1 cm high and 20 cm long. The results call into
question the early-summer's classification as the beginning of the
Titan's windy season, because high winds probably would have made for
larger waves. Information on Titan's climate is essential for sending
a probe safely to the surface. Although there are no formal plans for
a mission, there are plenty of concepts being developed by researchers
around the world. The study indicates that if a future mission lands
in early summer, there is a good chance that it will have a smooth
landing.


METHANOL DETECTED AROUND ENCELADUS
RAS

A serendipitous detection around Enceladus, an intriguing moon of
Saturn, of the organic molecule methanol suggests that material spewed
from Enceladus undertakes a complex chemical journey once it is vented
into space. This is the first time that a molecule from Enceladus has
been detected with a ground-based telescope. Enceladus's plumes are
thought to originate in water escaping from a sub-surface ocean
through cracks in the moon's icy surface. Eventually the plumes feed
into Saturn's second-outermost ring, the E-ring. Recent discoveries
that icy moons in the outer Solar System could host oceans of liquid
water and ingredients for life have sparked exciting possibilities for
their habitability. But, in this case, the findings suggest that the
methanol is being created by further chemical reactions once the plume
is ejected into space, making it unlikely that it is an indication of
life on Enceladus. Past studies of Enceladus have involved the
Cassini spacecraft, which detected molecules like methanol by flying
directly into the plumes. Recent work has found that the Earth's
oceans have amounts of methanol similar to that in Enceladus' plumes.

In the reported study, astronomers detected a bright methanol
signature with the IRAM 30-metre radio telescope in the Spanish Sierra
Nevada. The observation was very surprising, since it was not the
main molecule astronomers were originally looking for in Enceladus'
plumes. The team suggests the unexpectedly large quantity of methanol
may have two possible origins: either a cloud of gas expelled from
Enceladus has been trapped by Saturn's magnetic field, or gas has
spread further out into the E-ring. In either case, the methanol has
been greatly enhanced compared to detections in the plumes. Cassini
will end its journey later this year, leaving remote observations
through ground- and space-based telescopes as the only possibilities
for exploring Saturn and its moons --- at least for now.


RE-MAKING PLANETS AFTER STAR DEATH
RAS

Astronomers may have found an answer to the 25-year-old question of
how planets form in the aftermath of a supernova explosion. The first
planets outside the Solar System were discovered 25 years ago -- not
around a normal star like the Sun, but instead orbiting a tiny, super-
dense 'neutron star'. Such remnants are left over after a supernova,
the titanic explosion of a star many times as massive as the Sun.
Such 'planets in the dark' have turned out to be very rare, and
astronomers are puzzled over where they come from. The supernova
explosion should destroy any pre-existing planets, so the neutron star
needs to capture more raw materials to form its new companions. The
after-death planets can be detected because their gravitational pull
alters the times of arrival of radio pulses from the neutron star, or
'pulsar', that otherwise pass by us extremely regularly. Astronomers
believe that they have found a way for that to happen. They started
looking for the raw materials soon after the pulsar planets were
announced. They had one target, the Geminga pulsar located 800 light-
years away in the constellation of Gemini. Astronomers thought they
had found a planet there in 1997, but later discounted it because of
glitches in the timing. The scientists observed Geminga with the
James Clerk Maxwell Telescope (JCMT), which operates at sub-millimetre
wavelengths, sited on Hawaii. The light the astronomers detected has
a wavelength of about half a millimetre, so it is invisible to the
human eye, and is only partially transmitted by the Earth's
atmosphere.

What scientists saw was very faint. They went back to it in 2013 with
the new camera SCUBA-2. Combining the two sets of data helped to
ensure they were not just seeing some faint artefacts. Both images
showed a signal towards the pulsar, plus an arc around it. That seems
to be like a bow-wave -- Geminga is moving incredibly fast through our
Galaxy, much faster than the speed of sound in interstellar gas.
Astronomers think that material gets caught up in the bow-wave, and
then some solid particles drift in towards the pulsar. Calculations
suggest that that trapped interstellar 'grit' adds up to at least a
few times the mass of the Earth -- so there could be enough raw
material to make future planets.


MILKY WAY MAY HAVE 100,000 MILLION BROWN DWARFS
Royal Astronomical Society

Our galaxy could have 100,000 million brown dwarfs or more, according
to work by an international team of astronomers. Brown dwarfs are
objects intermediate in mass between stars and planets, with masses
too low to sustain stable hydrogen fusion in their cores (the hallmark
of stars like the Sun).

After the initial discovery of brown dwarfs in 1995, scientists
quickly realised that they are a natural by-product of processes that
primarily lead to the formation of stars and planets. All of the
thousands of brown dwarfs found so far are relatively close to the
Sun, the overwhelming majority within 1500 light-years, simply because
they are faint and therefore difficult to observe. Most of those
detected are located in nearby star-forming regions, which are all
fairly small and have a low density of stars. In 2006 the team began
a new search for brown dwarfs, observing five 'nearby' star-forming
regions. The Substellar Objects in Nearby Young Clusters (SONYC)
survey included the star cluster NGC 1333, 1000 light-years away in
the constellation Perseus. That object had about half as many brown
dwarfs as stars, a higher proportion than had been seen elsewhere.

To establish whether NGC 1333 was unusual, in 2016 the team turned to
another, more distant, star cluster, RCW 38, in the constellation
Vela. RCW 38 has a high density of more massive stars, and very
different conditions from other clusters. It is 5500 light-years
away, so the brown dwarfs are not only faint but are hard to pick out
next to the brighter stars. To get a clear image, the team used the
NACO adaptive-optics camera on ESO's Very Large Telescope, observing
the cluster for a total of 3 hours, and combining that picture with
earlier ones. The researchers found just as many brown dwarfs in
RCW 38 as in NGC 1333 -- about half as many as there are stars --
and tentatively concluded that the environment where the stars form,
whether stars are more or less massive, tightly packed or less
crowded, has only a small effect on how brown dwarfs form. From the
SONYC survey, it is estimated that our Galaxy, the Milky Way, has a
minimum of between 25,000 and 100,000 million brown dwarfs. There are
many smaller, fainter brown dwarfs too, so that could be a significant
underestimate, and the survey confirms that brown dwarfs are
ubiquitous.


FASTEST STARS IN MILKY WAY ARE FROM ANOTHER GALAXY
RAS

A group of astronomers has shown that the fastest-moving stars in our
Galaxy -- which are travelling so fast that they can escape from the
Milky Way altogether -- are in fact runaways from a much smaller
galaxy in orbit around our own. The researchers used data from the
Sloan Digital Sky Survey, and computer simulations, to demonstrate
that the stars concerned originated in the Large Magellanic Cloud
(LMC), a dwarf galaxy in orbit around the Milky Way. The fast-moving
stars, known as hyper-velocity stars, were able to escape their
original home when the explosion of one star in a binary system caused
the other to fly off with such speed that it was able to escape the
gravity of the LMC and get absorbed into the Milky Way. Astronomers
at first thought that the hyper-velocity stars, which are large blue
stars, may have been expelled from the centre of the Milky Way by a
super-massive black hole. Other scenarios involving disintegrating
dwarf galaxies or chaotic star clusters can also account for the
speeds of the stars, but all three mechanisms fail to explain why they
are found only in a certain part of the sky. To date, roughly 20
hyper-velocity stars have been observed, mostly in the northern
hemisphere, although it is possible that there are many more that
could be observed only from the southern hemisphere.

An alternative explanation of the origin of hyper-velocity stars is
that they are runaways from binary systems. In binary star systems,
the closer the two stars are, the faster they orbit one another. If
one star explodes as a supernova, it can break up the binary and the
remaining star flies off at almost the speed at which it was orbiting.
The escaping star is known as a runaway. Runaway stars originating in
the Milky Way are not fast enough to be 'hyper-velocity' because blue
stars can not orbit sufficiently close together without the two stars
merging. But a fast-moving galaxy could give rise to such speedy
stars. The LMC is the largest and fastest of the dozens of dwarf
galaxies in orbit around the Milky Way. It has only 10% of the mass
of the Milky Way, and so the fastest runaways born in it can easily
escape its gravity. The LMC flies around the Milky Way at 400 km/s,
and the velocity of runaway stars is the velocity at which they were
ejected plus the velocity of the LMC. That can be fast enough for
them to be the hyper-velocity stars. It also explains their position
in the sky, because the fastest runaways are those ejected 'forward'
along the orbit of the LMC towards the constellations Leo and Sextans.


SUPER-MASSIVE BLACK HOLE SUFFERS FROM 'INDIGESTION'
RAS

A multi-wavelength study of a pair of colliding galaxies has revealed
the cause of a super-massive black hole's case of 'indigestion'. Once
every couple of hundred million years, the small galaxy NGC 5195 falls
into the outer arms of its larger companion, NGC 5194, also known as
the Whirlpool Galaxy. The two galaxies are locked in a gravitational
embrace that will ultimately result in ther combining into a single
galaxy. As NGC 5195 plunges into the Whirlpool, matter streams onto
the super-massive black hole at NGC 5195's centre and forms an
accretion disc. The disc grows to a point at which the black hole can
no longer accrete or 'digest' efficiently, and matter is blasted out
into the surrounding interstellar medium. Last year, the Chandra
X-Ray observatory observed arcs of X-ray emission that appeared to
result from such activity. Now, new high-resolution images of the
core of NGC 5195, taken with the e-MERLIN radio array, and archive
images of the surrounding area from the Very Large Array (VLA),
Chandra, and the Hubble space telescope, reveal in detail how the
blasts occur and spread. The study was led by astronomers at Jodrell
Bank.

The black hole at the centre of NGC 5195 has a mass equivalent to 19
million Suns. When the accretion process breaks down, immense forces
and pressures create a shock wave that pushes matter out into the
interstellar medium. Electrons, accelerated close to the speed of
light, interact with the magnetic field of the interstellar medium and
emit energy at radio wavelengths. The shock wave then inflates and
heats up the interstellar medium, which emits in the X-ray band, and
strips the electrons from surrounding neutral hydrogen atoms to make
ionized hydrogen gas. The inflated bubble creates the arcs detected
by Chandra and Hubble. Comparing the VLA images at radio wavelengths
to Chandra's X-ray observations and the hydrogen-emission detected by
Hubble shows that features in the very different wavelength domains
are not only connected, but that the radio outflows are in fact the
progenitors of the structures seen by Chandra and Hubble. The
activity in NGS 5195 is an event of galactic proportions that we can
see right across the electromagnetic spectrum. The age of the arcs in
NGC 5195 is 1-2 million years. To put that into context, the first
traces of matter were being forced out of the black hole in that
system at about the time that our ancestors were learning to make
fire. That we are able to observe the (celestial) event now through
such a range of astronomical facilities is quite remarkable.


ASTRONOMERS GET RARE CHANCE TO SEE GALAXY DEMISE
RAS

A primitive galaxy that could provide clues about the early Universe
has been observed by astronomers as it begins to be consumed by a
gigantic neighbouring galaxy. The Little Cub galaxy -- so called
because it sits in the Ursa Major or Great Bear constellation! -- is
being stripped of the gas that it needs to continue forming stars by
its larger companion. The find gives scientists a rare opportunity
to observe a dwarf galaxy as its gas is removed by the effects of a
nearby giant galaxy, to learn more about how that process happens.
As the Little Cub has remained almost pristine since its formation,
scientists also hope that its elements will reveal more about the
chemical signature of the Universe just minutes after the Big Bang.
The Little Cub and its larger neighbour, a 'grand-design' spiral
galaxy called NGC 3359, are about 200 to 300 thousand light-years
apart, and approximately 50 million light-years away. Gas from the
Little Cub is being stripped away by its interaction with NGC 3359,
which has up to 10,000 times as many stars as the Little Cub and is
similar to our Milky Way. By observing the pair, scientists hope to
understand more about how and when gas is lost from smaller galaxies.

It is rare for such a tiny galaxy still to contain gas and be forming
stars when it is in close proximity to a much larger galaxy, so this
is a great opportunity to see how that process works. Essentially the
larger galaxy is removing the fuel that the Little Cub needs to form
stars, which will eventually shut down star formation and lead to the
smaller galaxy's demise. The researchers also hope to gain an insight
into the make-up of the very early Universe, by studying the hydrogen
and helium atoms that are being illuminated by the small number of
very bright stars within the 'Little Cub' -- which also has the less
romantic name SDSS J1044+6306. Astronomers know from studies of the
chemistry of the Little Cub that it is one of the most primitive
objects currently known in our cosmic neighbourhood. Such galaxies,
which have remained dormant for most of their lives, are believed to
contain the chemical elements forged a few minutes after the Big Bang.
By measuring the relative number of hydrogen and helium atoms in the
Little Cub, we might be able to learn more about what made up the
Universe in the moments after it began 13.7 thousand million years
ago.

The Little Cub was initially identified as a potentially pristine
dwarf galaxy in data from the Sloan Digital Sky Survey (SDSS).
Follow-up observations were conducted with the 3-m Shane Telescope at
Lick Observatory and the 10-m Keck telescope.


HUBBLE PUSHED BEYOND LIMITS
NASA/Goddard Space Flight Center

When it comes to the distant Universe, even the Hubble telescope can
go only so far. Teasing out finer details requires clever thinking
and a little help from a cosmic alignment with a gravitational lens.
By applying a new computational analysis to a galaxy magnified by a
gravitational lens, astronomers have obtained images 10 times sharper
than Hubble could achieve on its own. The results show an edge-on disc
galaxy studded with brilliant patches of newly formed stars. The
galaxy in question is so far away that we see it as it appeared 11,000
million years ago, 'only' 2700 million years after the Big Bang. It
is one of more than 70 strongly lensed galaxies studied by the Hubble
telescope, following up targets selected by the Sloan Giant Arcs
Survey, which discovered hundreds of strongly lensed galaxies by
searching Sloan Digital Sky Survey imaging data covering one-fourth of
the sky. The gravity of a giant cluster of galaxies between the
observed galaxy and the Earth distorts the more distant galaxy's
light, stretching the appearance of the galaxy into an arc and also
magnifying it almost 30 times. The team developed a special computer
code to remove the distortions caused by the gravitational lens and
reveal the disc galaxy as it would normally appear.

The resulting reconstructed image revealed two dozen clumps of newborn
stars, each spanning about 200 to 300 light-years. That flew in the
face of theories suggesting that star-forming regions in the distant,
early Universe were much larger, 3,000 light-years or more in size.
Without the magnification boost of the gravitational lens, the disc
galaxy would appear perfectly smooth and unremarkable to Hubble, and
would give astronomers a very different picture of where stars are
forming. While Hubble highlighted new stars within the lensed galaxy,
the upcoming James Webb space telescope could be expected to uncover
older, redder stars that formed even earlier in the galaxy's history.
It will also see through any obscuring dust within the galaxy.

ENB 447

Clive

JUPITER NOW HAS 69 KNOWN MOONS
Nature World News

A new study has shown that Jupiter, the biggest planet in the Solar
System, has at least 69 moons. The U.S. Department of Terrestrial
Magnetism said that the study, which was originally conducted to
survey distant objects within the Kuiper Belt and beyond Pluto, also
aimed to look for new planets such as Planet X. It just so happened
that Jupiter was within the area in which the research was conducted
in March 2016 and March 2017. The research imaged fields near
Jupiter, offering a chance to examine the regions near the planet and
to look for its moons. The already-known moons were detected as well
as new ones. Some previously-detected ones had been 'lost' but were
re-discovered, and some not previously known were seen for the first
time. In March 2016 and 2017, S/2016 J1 and S/2017 J1 were observed,
respectively. It has been confirmed that those are not already-
observed but 'lost' objects, but are two 'new' moons that are now
included in the total of 69. There could still be other new Jupiter
moons detected in the observations, but the researchers want to re-
observe and confirm them first in 2018 to know for sure.

In 2003, there were several known Jupiter moons that were believed to
have been lost and were never recognized again until now. There was
too little information available about their orbits, so it was not
possible to predict where they should be at any given time. In 2016,
there were 14 'lost' Jupiter moons. In the new study, five of the 14
lost moons were found. The researchers believe that they could have
found all 14 of them, but it would require further analysis to cross-
check if they were indeed the lost ones or were newly discovered ones.


DID OUR SUN HAVE A TWIN?
University of California at Berkeley

Did our Sun have a twin when it was born 4.5 billion years ago?
Almost certainly yes -- though not an identical twin. And so did
every other Sunlike star in the Universe, according to a new analysis
by a theoretical physicist from the University of California at
Berkeley, and a radio astronomer from the Smithsonian Astrophysical
Observatory at Harvard. Many stars have companions, including our
nearest neighbour, Alpha Centauri, a triple system. Astronomers have
long sought an explanation. Are binary and triple star systems born
that way? Did one star capture another? Do binary stars sometimes
split up and become single stars? Astronomers have even searched for
a companion to our Sun, a star dubbed Nemesis because it was supposed
to have kicked into the Earth's orbit an asteroid that collided with
our planet and exterminated the dinosaurs. But it has never been
identified. The new assertion is based on a radio survey of a giant
molecular cloud filled with recently formed stars in the constellation
Perseus, and a mathematical model that can explain the Perseus
observations only if all Sun-like stars are born with a companion.
The astronomers ran a series of statistical models to see if they
could account for the relative populations of young single stars and
binaries of all separations in the Perseus molecular cloud, and the
only model that could reproduce the data was one in which all stars
form initially as wide binaries. Those systems then either shrink or
break apart within a million years. In that study, 'wide' means that
the two stars are separated by more than 500 astronomical units (AU).
(1 AU is the average distance between the Sun and the Earth.) A wide
binary companion to the Sun would have been at least 17 times farther
from the Sun than Neptune. On the basis of that model, the Sun's
sibling most likely escaped and mixed with all the other stars in our
region of the Milky Way galaxy, never to be recognized. Astronomers
have speculated about the origins of binary- and multiple-star systems
for hundreds of years, and in recent years have created computer simu-
lations of collapsing masses of gas to understand how they condense
under gravity into stars. They have also simulated the interaction of
many young stars recently freed from their gas clouds. Several years
ago, one such simulation at the University of Bonn led astronomers to
conclude that all stars are born as binaries.

Yet direct evidence from observations has been scarce. As astronomers
look at younger and younger stars, they find a greater proportion of
binaries, but why is still a mystery. Astronomers have known for
several decades that stars are born inside egg-shaped cocoons called
dense cores, which are sprinkled throughout immense clouds of cold,
molecular hydrogen that are the nurseries for young stars. Through an
optical telescope, such clouds look like holes in the starry sky,
because the dust accompanying the gas blocks light from both the stars
forming inside and the stars behind. The clouds can, however, be
probed by radio telescopes, since the cold dust grains in them emit at
radio wavelengths, and radio waves are not blocked by the dust. The
Perseus molecular cloud is one such stellar nursery, about 600 light-
years away and about 50 light-years long. Last year, a team of
astronomers completed a survey that used the Very Large Array, a
collection of radio dishes in New Mexico, to look at star formation
inside the cloud. Called VANDAM, it was the first complete survey of
all young stars in a molecular cloud, that is, stars less than about
4 million years old, including both single and multiple stars down to
separations of about 15 astronomical units. It captured all multiple
stars with a separation of more than about the radius of Uranus' orbit
-- 19 AU -- in the Solar System. The VANDAM survey produced a census
of all Class 0 stars -- those less than about 500,000 years old -- and
Class I stars -- those between about 500,000 and 1 million years old.
Both types of stars are so young that they are not yet burning
hydrogen to produce energy. The results from VANDAM were combined
with additional observations that reveal the egg-shaped cocoons around
the young stars. Those additional observations come from the Gould
Belt Survey with SCUBA-2 on the Maxwell Telescope in Hawaii. From
those data, it was discovered that all of the widely separated binary
systems -- those with stars separated by more than 500 AU -- were very
young systems, containing two Class 0 stars. Those systems also
tended to be aligned with the long axis of the egg-shaped dense core.
The slightly older Class I binary stars were closer together, many
separated by about 200 AU, and showed no tendency to align along the
egg's axis. There is an implication that each dense core, which
typically comprises a few solar masses, converts twice as much
material into stars as was previously thought.


TEN EARTH-SIZE PLANETS WITHIN HABITABLE ZONE
NASA

The Kepler space-telescope team has produced a catalogue that lists
219 new planet candidates, 10 of which are of near-Earth size and
orbiting in their respective stars' habitable zones -- the range of
distance from a star where liquid water could pool on the surface of a
rocky planet. It is a comprehensive and detailed catalogue of candi-
date exo-planets (planets outside the Solar System), from Kepler's
first four years of data. It is also the final catalogue from the
spacecraft's view of a patch of sky in the constellation Cygnus. With
the release of that catalogue, derived from data publicly available on
the NASA Exo-planet Archive, there are now 4,034 planet candidates
identified by Kepler, of which 2,335 have been verified as exo-planets.
Of roughly 50 near-Earth-size habitable-zone candidates detected by
Kepler, more than 30 have been verified. Additionally, results using
Kepler data suggest two distinct size groupings of small planets.
Both results have significant implications for the search for life.
The final Kepler catalogue will serve as the foundation for more study
to determine the prevalence and demographics of planets in the Galaxy,
while the discovery of the two distinct planetary populations shows
that about half the planets we know of in the Galaxy either have no
surface, or one that lies beneath a deep, crushing atmosphere --
environments unlikely to encourage life. The Kepler space telescope
hunts for planets by detecting the minuscule drop in a star's
brightness that occurs during a transit, when a planet crosses in
front of it.

This is the eighth instalment of the Kepler candidate catalogue,
gathered by re-processing the entire set of data from Kepler's
observations during the first four years of its primary mission.
The data are expected to go some way towards enabling scientists to
determine what planetary populations -- from rocky bodies the size of
the Earth, to gas giants the size of Jupiter -- make up the Galaxy's
planetary demographics. To try to ensure that many planets were not
missed, the team introduced their own simulated planet-transit signals
into the data set and determined how many their software identified as
planets. Then they added spoof data such as might appear to come from
a planet, but were actually false signals, and checked how often the
analysis mistook them for actual planet candidates. Those experiments
indicated which types of planets were over-counted and which were
under-counted by the Kepler team's data-processing methods.


FIRST BLACK-HOLE VISUAL BINARY?
National Radio Astronomy Observatory

Astronomers using the Very-Long-Baseline Array (VLBA) have made the
first detection of orbital motion in a pair of super-massive black
holes in a galaxy some 750 million light-years away. The object, an
elliptical galaxy, called 0402+379 after its location in the sky, was
first observed in 1995. The two black holes, with a combined mass
15 billion times that of the Sun, are probably separated by 'only'
about 24 light-years, extremely close for such a system. This is the
first pair of black holes to be seen as separate objects that are
moving with respect to each other, so this is the first black-hole
'visual' binary. Super-massive black holes, with millions of times
the mass of the Sun, are thought to reside at the cores of most
galaxies. The presence of two such monsters at the centre of a single
galaxy is taken to mean that two galaxies merged with one another some
time in the past. In such a case, the two black holes themselves may
eventually merge in an event that would produce gravitational waves
that would ripple out across the Universe. Researchers believe that
millions of years into the future the two super-massive black holes in
0402+379 will merge. The latest research incorporates new VLBA
observations from 2009 and 2015, along with re-analysis of earlier
VLBA data. This work has revealed motion of the two cores, confirming
that the two black holes are orbiting one another. The scientists'
initial calculations indicate that they complete a single orbit in
about 30,000 years. The astronomers also hope to discover other such
systems. The galaxy mergers that bring two super-massive black holes
close together are considered to be a common process in the Universe,
so astronomers expect that such binary pairs ought to be common.


MASSIVE DEAD DISC GALAXY FOUND
NASA/Goddard Space Flight Center

By combining the power of a 'natural lens' in space with the capabil-
ity of the Hubble telescope, astronomers made a surprising discovery
-- the first example of a compact yet massive, fast-spinning, disc-
shaped galaxy that stopped making stars 'only' a few thousand million
years after the 'Big Bang'. Finding such a galaxy early in the
history of the Universe challenges the current understanding of how
massive galaxies form and evolve. When Hubble photographed the
galaxy, astronomers expected to see a chaotic ball of stars formed
through galaxies merging together. Instead, they saw evidence that
the stars were born in a pancake-shaped disc. This is the first
direct observational evidence that at least some of the earliest
so-called 'dead' galaxies -- where star formation stopped -- somehow
evolve from Milky-Way-shaped discs into the giant elliptical galaxies
we see today. This is a surprise because elliptical galaxies contain
older stars, while spiral galaxies typically contain younger blue
stars. At least some of the early 'dead' disc galaxies must have gone
through major make-overs. They not only changed their structure, but
also the motions of their stars to make the shape of an elliptical
galaxy. Previous studies of distant dead galaxies have assumed that
their structure is similar to the local elliptical galaxies they will
evolve into. Confirming that assumption in principle requires more
powerful space telescopes than are currently available. However,
through the phenomenon known as gravitational lensing, a massive,
foreground cluster of galaxies acts as a natural lens in space by
magnifying and stretching images of more-distant background galaxies.
By supplementing such a natural lens with the resolving power of
Hubble, scientists were able to see into the centre of the dead
galaxy.

The remote galaxy is three times as massive as the Milky Way but only
half the size. Rotational-velocity measurements made with the
European Southern Observatory's Very Large Telescope (VLT) showed that
the disc galaxy is spinning more than twice as fast as the Milky Way.
Using archival data from the Cluster Lensing And Supernova survey with
Hubble (CLASH), astronomers were able to determine the stellar mass,
star-formation rate, and the ages of the stars. Why that galaxy
stopped forming stars is still unknown. It may be the result of an
active galactic nucleus, where energy is gushing from a super-massive
black hole; such energy inhibits star formation by heating the gas or
expelling it from the galaxy. Or it may be the result of the cold gas
streaming onto the galaxy being rapidly compressed and heated up, pre-
venting it from cooling down into star-forming clouds in the galaxy's
centre. But how do young, massive, compact discs evolve into the
elliptical galaxies we see in the present-day Universe? If those
galaxies grow through merging with minor companions, and the minor
companions come in large numbers and from all sorts of different
angles onto the galaxy, that would eventually randomize the orbits of
stars in the galaxies. Major mergers would definitely also destroy
the ordered motion of the stars.

ENB 446

Clive

ASTEROID-HUNTING SPACECRAFT SUCCESS
NASA

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE)
mission has released its third year of survey data, with the space-
craft discovering 97 previously unknown celestial objects in the
last year. Of those, 28 were near-Earth objects, 64 were main-belt
asteroids, and five were comets. The spacecraft has now characterized
a total of 693 near-Earth objects since the mission was re-started in
2013 December. Of those, 114 are new. NEOWISE is not only discovering
previously uncharted asteroids and comets, but it is providing
excellent data on many of those already known. Near-Earth objects
(NEOs) are comets and asteroids that have been nudged by the
gravitational attraction of the planets in the Solar System into
orbits that cause them to enter the Earth's neighbourhood. Ten of the
objects discovered by NEOWISE in the past year have been classified as
potentially hazardous asteroids, on the basis of their sizes and orbits.

More than 2.6 million infrared images of the sky were collected in the
third year of operations by NEOWISE. Those data are combined with the
first two years' NEOWISE data into a single archive that contains
approximately 7.7 million sets of images and a data base of more than
57.7 (US-)billion source detections extracted from those images. The
NEOWISE images also contain glimpses of rare objects, like comet
C/2010 L5 WISE. A new technique of modelling comet behaviour, called
tail-fitting, showed that that particular comet experienced a brief
outburst as it swept through the inner Solar System. The tail-
fitting technique identifies the size and quantity of dust particles
in the vicinity of the comet, and when they were ejected from the
comet's nucleus, revealing the history of the comet's activity. With
tail-fitting, future all-sky surveys may be able to find and collect
data on more cometary-outburst activity when it happens.

Originally called the Wide-field Infrared Survey Explorer (WISE), the
spacecraft was launched in 2009 December. It was placed in hiber-
nation in 2011 after its primary astrophysical mission was completed.
In 2013 September it was re-activated, re-named NEOWISE and assigned
a new mission: to assist NASA's efforts to identify the population of
potentially hazardous near-Earth objects. NEOWISE is also character-
izing more distant populations of asteroids and comets to provide
information about their sizes and compositions.


ENCELADUS MAY HAVE TIPPED OVER
NASA

Saturn's icy, ocean-bearing moon Enceladus may have tipped over in the
distant past, according to recent research from the Cassini mission.
Researchers found evidence that the moon's spin axis -- the line
through the north and south poles -- has re-oriented, possibly owing
to a collision with a smaller body, such as an asteroid. Examining
the moon's features, the team showed that Enceladus appears to have
tipped away from its original axis by about 55 degrees -- more than
halfway toward rolling completely onto its side. Cassini found a
chain of low areas, or basins, that trace a belt across the moon's
surface that researchers believe are the fossil remnants of an earlier
equator and poles. The area around the icy moon's current south pole
is an active region where long, linear fractures referred to as 'tiger
stripes' slice across the surface. Scientists speculate that an
asteroid may have struck the region in the past when it was closer to
the equator.

In 2005, Cassini discovered that jets of water vapour and icy
particles spray from the tiger-stripe fractures -- evidence that an
underground ocean is venting directly into space from beneath the
active south-polar surface. Whether it was caused by an impact or
some other process, astronomers think that the disruption and creation
of the tiger-stripe landform caused some of Enceladus' mass to be
redistributed, making the moon's rotation unsteady and wobbly. The
rotation would eventually have stabilized, probably taking more than a
million years to do so. By the time that the rotation settled down,
the north-south axis would have re-oriented to pass through different
points on the surface -- a mechanism researchers call 'true polar
wander'. The polar-wander idea could explain why Enceladus' modern-
day north and south poles appear quite different. The south is active
and topographically young, while the north is covered in craters and
appears much older. The moon's original poles would have looked more
alike before the event that caused Enceladus to tip over and relocate
the disrupted tiger-stripe landform to the moon's south-polar region.


INGREDIENT OF LIFE FOUND AROUND SUN-LIKE STARS
RAS

Using the Atacama Large Millimetre / submillimetre Array (ALMA),
astronomers have observed stars like the Sun at very early stages in
their formation and found traces of methyl isocyanate -- a chemical
building-block of life. This is the first-ever detection of that
pre-biotic molecule towards solar-type proto-stars, the sort from
which our Solar System evolved. The discovery could help scientists
understand how life arose on Earth. Two teams of astronomers detected
the methyl isocyanate in the multiple-star system IRAS 16293-2422.

ALMA's capabilities allowed both teams to observe the molecule at
several different and characteristic wavelengths across the radio
spectrum. They found the unique chemical fingerprints located in the
warm, dense inner regions of the cocoon of dust and gas surrounding
young stars in their earliest stages of evolution. Each team
identified and isolated the signatures of methyl isocyanate. They
followed that up with computer chemical modelling and laboratory
experiments to refine their understanding of the molecule's origin.
IRAS 16293-2422 is a multiple system of very young stars, around 400
light-years away, in a large star-forming region called Rho Ophiuchi.
The new results from ALMA show that methyl isocyanate gas surrounds
each of the young stars. The Earth and the other planets in the Solar
System formed from the material left over after the formation of the
Sun. Studying solar-type proto-stars can therefore open a window to
the past for astronomers and allow them to observe conditions similar
to those that led to the formation of our Solar System over 4.5 billion years
ago.


COLLAPSING STAR GIVES BIRTH TO BLACK HOLE
NASA

Astronomers used the combined power of the Large Binocular Telescope
(LBT) and the Hubble and Spitzer space telescopes, to look for
remnants of a vanished star, only to find that it disappeared out of
sight. The star, which was 25 times the mass of the Sun, should have
exploded in a very bright supernova. Instead, it fizzled out -- and
then left behind a black hole. 'Massive fails', like that one in a
'nearby' galaxy, could explain why astronomers rarely see supernovae
from the most massive stars. As many as 30% of such stars, it seems,
may quietly collapse into black holes -- no supernova required. The
typical view is that a star can form a black hole only after it goes
supernova. If a star can fall short of a supernova and still make a
black hole, that would help to explain why we don't see supernovae
from the most massive stars. Among the galaxies that have been
watched is NGC 6946, a spiral galaxy 22 million light-years away that
is nicknamed the 'Fireworks Galaxy' because supernovae frequently
happen there -- indeed, one, SN 2017eaw, was discovered as recently as
May 14. Starting in 2009, one particular star, named N6946-BH1, began
to brighten weakly. By 2015, it appeared to have winked out of
existence. After the LBT survey for failed supernovae turned up the
star, astronomers aimed the Hubble and Spitzer space telescopes to see
if it was still there but merely dimmed. They also used Spitzer to
search for any infrared radiation emanating from the spot. That would
have been a sign that the star was still present, but perhaps just
hidden behind a dust cloud. All the tests came up negative. The star
was no longer there. By a process of elimination, the researchers
eventually concluded that the star must have become a black hole. It
is too early in the project to know how often stars experience massive
failures, but astronomers are able to make a preliminary estimate.

N6946-BH1 is the only probable failed supernova found in the first
seven years of the survey. During that time, six normal supernovae
have occurred within the galaxies monitored, suggesting that 10 to 30
per cent of massive stars die as failed supernovae. That is just the
fraction that would explain the very problem that motivated the
observers to start the survey, that is, that there are fewer observed
supernovae than should be occurring if all massive stars die that way.
The really interesting part of the discovery is the implications that
it holds for the origins of very massive black holes -- the kind that
the LIGO experiment* detected via gravitational waves. It does not
necessarily make sense that a massive star could become a supernova
-- a process which entails blowing off much of its outer layers -- and
still have enough mass left over to form a massive black hole on the
scale of those that LIGO detected. It may be much easier to under-
stand how a very massive black hole is made if there is no supernova.

*LIGO is the Laser Interferometer Gravitational-Wave Observatory.


GALAXY ALIGNMENTS TRACED BACK 10 BILLION YEARS
University of Turku

A new study reveals that the most massive galaxies in the Universe
have been aligned with their surroundings for at least ten billion years.
That discovery shows that galaxies, like people, are influenced by their
environment from a young age. Astronomers have long known that
galaxies cluster together into enormous systems -- the urban centres of
the cosmos -- and that the largest galaxies tend to 'point' towards their
neighbours. But how and when those alignments occur remains a mystery.
Using the Hubble Space Telescope, the international team of collaborators
observed 65 distant galaxy clusters whose light has taken billions of years to
reach the Earth. They showed for the first time that the largest galaxies in those systems
were already aligned with their surroundings when the Universe was
only 1/3 of its current age. Although clusters have hundreds or
thousands of member galaxies, most are randomly oriented in space.
Only the biggest galaxies are aligned with their surroundings, which
suggests that they are especially sensitive to their environment.
The team is eager to look further back in time by observing more
remote clusters, but studying galaxies at the dawn of time is not
easy, even with Hubble.


CONTRACTS FOR THE ELT'S GIANT MIRROR SIGNED
ESO

Contracts for the manufacture of the 39-metre primary mirror of ESO's
Extremely Large Telescope have been signed at the ESO headquarters
near Munich. The German company SCHOTT will produce the blanks of
the mirror segments, and the French company Safran Reosc will polish,
mount and test the segments. The contract to polish the mirror blanks
is the second-largest contract for the ELT construction and the third-
largest contract ESO has ever awarded. The unique optical system of
the Extremely Large Telescope consists of five mirrors, each of which
presents its own significant engineering challenge. The 39-metre-
diameter primary mirror, which will be made up of 798 individual
hexagonal segments each measuring 1.4 metres across, will be by far
the largest ever made for an optical telescope. Together, the
segments will collect tens of millions of times as much light as the
human eye. Once the mirror blanks are ready they will be passed to
Safran Reosc, who will design the mounting interfaces, polish and
figure the segments, integrate them into their support systems, and
perform optical tests before delivery. During the polishing process,
each segment will be polished until it has no surface irregularity
greater than about 10 nanometres. Both SCHOTT and Safran Reosc have
already had long and successful involvements with ESO. Together they
manufactured many optical components, including the 8.2-metre main
mirrors of the four Unit Telescopes of the ESO Very Large Telescope.
The ELT is currently under construction at Cerro Armazones near the
Paranal Observatory in northern Chile, and is scheduled to see first
light in 2024.


Bulletin compiled by Clive Down



ENB 445

Clive

THIRD-LARGEST DWARF PLANET HAS MOON
NASA/Goddard Space Flight Center

The combined power of three space observatories, including the
Hubble Space Telescope, has helped astronomers discover a moon
orbiting the third-largest dwarf planet, catalogued as 2007 OR10.
The pair resides in the frigid outskirts of the Solar System
called the Kuiper Belt, a realm of icy debris left over from the
system's formation 4.6 billion years ago. With this discovery,
most of the known dwarf planets in the Kuiper Belt larger than
600 miles across have companions. Those bodies provide insight
into how moons formed in the young Solar System. The discovery
of satellites around all of the known large dwarf planets (except
for Sedna) means that, when those bodies formed, a very long time
ago, collisions must have been more frequent, and that is a
constraint on the formation models. If there were frequent
collisions, then it was quite easy to form satellites. The
objects most likely slammed into one another more often because
they inhabited a crowded region. But the speed of the colliding
objects could not have been too fast or too slow, according to
the astronomers. If the impact velocity were too great, the
smash-up would have created lots of debris that could have
escaped from the system; if too slow, the collision would have
produced only an impact crater.

The team discovered the moon in archival images of 2007 OR10
taken by Hubble's Wide-Field Camera 3. Observations taken of the
dwarf planet by the Kepler space telescope first tipped off the
astronomers to the possibility of a moon circling it. Kepler
revealed that 2007 OR10 has a slow rotation period of 45 hours.
Typical rotation periods for Kuiper-Belt Objects are under 24
hours. The team looked in the Hubble archive because the slower
rotation period could have been caused by the gravitational
effect of a moon. The initial investigator missed the moon in
the Hubble images because it is very faint. The astronomers
observed the moon in two separate Hubble observations spaced a
year apart. The images show that the moon is gravitationally
bound to 2007 OR10 because it moves with the dwarf planet, as
seen against a background of stars. However, the two observa-
tions did not provide enough information for the astronomers to
determine an orbit. They calculated the diameters of both
objects on the basis of observations in far-infrared light by
the Herschel Space Observatory, which measured their thermal
emission. The dwarf planet is about 950 miles across, and its
moon is estimated to be 150--250 miles in diameter. 2007 OR10,
like Pluto, follows an eccentric orbit, and is currently three
times farther from the Sun than Pluto is. 2007 OR10 is a member
of the exclusive club of 'dwarf planets', of which there are
nine. Of those bodies, only Pluto and Eris are larger.


'DETERGENT' MOLECULES MAY DRIVE METHANE CHANGES
NASA

A new study finds that recent increases in global methane levels
observed since 2007 are not necessarily due to increasing
emissions, but instead may be due to changes in how long methane
remains in the atmosphere after it is emitted. The second-most-
important human-produced greenhouse gas after carbon dioxide,
methane is colourless, odourless and can be hard to track. The
gas has a wide range of sources, from decomposing biological
material to leaks in natural-gas pipelines. In the early 2000s,
atmospheric scientists studying methane found that its global
concentration -- which had increased for decades, driven by
methane emissions from fossil fuels and agriculture -- levelled
off as the sources of methane reached a balance with its
destruction mechanisms. The methane levels remained stable for a
few years, then unexpectedly started rising again in 2007, a
trend that is still continuing. Previous studies of the renewed
increase have focused on high-latitude wetlands or fossil fuels,
Asian agricultural growth, or tropical wetlands as potential
sources of the increased emissions. But the new study suggests
that methane emissions might not have increased dramatically
since 2007 after all.

The researchers used long-term measurements of methane, its
isotopes and 1,1,1-trichloroethane (a compound that serves as a
proxy for estimating how long methane remains in the atmosphere)
from numerous global ground stations. From those data, the
scientists were able to determine sources of methane and how
quickly it is destroyed in the Earth's atmosphere. They found
that the most likely explanation for the recent increase has less
to do with methane emissions than previously thought and more to
do with changes in the availability of the hydroxyl radical (OH),
which breaks down methane in the atmosphere. The amount of
hydroxyl in the atmosphere has an impact on global methane
concentrations. If global levels of hydroxyl decrease, global
methane concentrations will increase -- even if methane emissions
remain constant. In tracking the observed changes in methane and
the inferred changes in hydroxyl, scientists noted that fluctua-
tions in hydroxyl concentrations can explain some of the recent
methane trends. However, the scientists cannot explain the
global changes in hydroxyl concentrations seen in the past
decade. They say that future independent studies are needed to
quantify year-to-year variations in the hydroxyl radical and
their potential drivers. They would also like to see the trends
they detected verified with more detailed studies of the sources
and the destruction mechanisms of methane, particularly in the
tropics.


A FAR-FLUNG MEMBER OF THE SOLAR SYSTEM
National Radio Astronomy Observatory

Using the Atacama Large Millimeter/submillimeter Array (ALMA),
astronomers have obtained extraordinary details about a recently
discovered far-flung member of the Solar System, the planetary
body 2014 UZ224, informally known as DeeDee. At about three
times the current distance of Pluto from the Sun, DeeDee is the
second-most-distant-known trans-Neptunian object (TNO) with a
confirmed orbit, surpassed only by the dwarf planet Eris.
Astronomers estimate that there are tens of thousands of such icy
bodies in the outer Solar System beyond the orbit of Neptune.
The new ALMA data reveal, for the first time, that DeeDee is
roughly 635 kilometres across, or about two-thirds the diameter
of Ceres, the largest member of the asteroid belt. At that size,
DeeDee should have enough mass to be spherical, the criterion
necessary for astronomers to consider it to be a dwarf planet,
though it has yet to receive that official designation.
Currently, DeeDee is about 92 astronomical units (AU) from the
Sun. It takes DeeDee more than 1,100 years to complete one
orbit; light from DeeDee takes nearly 13 hours to reach the
Earth.

The object was discovered with the 4-metre Blanco telescope at
the Cerro Tololo Inter-American Observatory in Chile as part of
ongoing observations for the 'Dark Energy Survey', that seeks to
understand the accelerating expansion of the Universe. The Dark
Energy Survey produces vast numbers of astronomical images, which
give astronomers the opportunity to search also for distant
Solar-System objects. The initial search, which includes nearly
15,000 images, identified more than a thousand million candidate
objects. The vast majority of them turned out to be background
stars and even-more-distant galaxies. A small fraction, however,
were observed to move slowly across the sky over successive
observations, the telltale sign of a TNO.

One such object was identified on 12 separate images. The
astronomers informally dubbed it DeeDee, which is short for
Distant Dwarf. The optical data from the Blanco telescope
enabled the astronomers to measure DeeDee's distance and orbital
properties, but they were unable to determine its size or other
physical characteristics. It was possible that DeeDee was a
relatively small member of the Solar System, yet reflective
enough to be detected. Alternatively, it could be uncommonly
large and dark, reflecting only a tiny portion of the feeble
sunlight that reaches it; both scenarios would produce identical
optical data. Since ALMA observes the cold, dark Universe, it is
able to detect the heat -- in the form of millimetre-wavelength
radiation -- emitted naturally by cold objects in space. The
heat signature from a distant Solar-System object would be
directly proportional to its size. By comparing the ALMA
observations to the earlier optical data, the astronomers had the
information necessary to calculate the object's size. Objects
like DeeDee are cosmic leftovers from the formation of the Solar
System. Their orbits and physical properties reveal important
details about the formation of planets, including the Earth.
This discovery shows that it is possible to detect very distant,
slowly moving objects in the Solar System. The researchers note
that the same technique might be used to detect the hypothesized
'Planet Nine' that may reside far beyond DeeDee and Eris.


STUDY SHOWS MOST HABITABLE PLANETS LACK DRY LAND
RAS

A new study has used a statistical model to suggest that most
habitable planets may be dominated by oceans spanning over 90% of
their surface area. The author of the study has constructed a
statistical model -- based on Bayesian probability -- to predict
the division between land and water on habitable exo-planets.
For a planetary surface to have extensive areas of both land and
water, a delicate balance must be struck between the volume of
water it retains over time, and how much space it has to store it
in its oceanic basins. Both of those quantities may vary
substantially across the full spectrum of water-bearing worlds,
and why the Earth's values are so well balanced is an unresolved
and long-standing conundrum. The model predicts that most
habitable planets will be dominated by oceans spanning over 90%
of their surface areas. That conclusion is reached because the
Earth itself is close to being a so-called 'water world' - a
world where all land is immersed under a single ocean. The new
work finds that the Earth's finely balanced oceans may be a
consequence of the 'anthropic principle' -- more often used in a
cosmological context -- which accounts for how our observations
of the Universe are influenced by the requirement for the
formation of sentient life. On the basis of the Earth's ocean
coverage of 71%, there is evidence supporting the hypothesis that
anthropic selection effects are at work.

To test the statistical model, feedback mechanisms were taken
into account, such as the deep-water cycle and erosion and
deposition processes. The study also proposes a statistical
approximation to determine the diminishing habitable land area
for planets with smaller oceans as they become increasingly
dominated by deserts. Why did we evolve on this planet and not
on one of the many other habitable worlds? In this study it is
suggested that the answer could be linked to a selection effect
involving the balance between land and water. Our understanding
of the development of life is far from complete, but it is not
quite so dire that we must adhere to the approximation that all
habitable planets have an equal chance of hosting intelligent
life.


SUPER-MASSIVE BLACK HOLES FOUND IN TINY GALAXIES
University of Utah

Three years ago, astronomers discovered that an ultra-compact
dwarf galaxy contained a super-massive black hole, then the
smallest known galaxy to harbour such a giant black hole. The
findings suggested that the dwarfs were probably tiny leftovers
of larger galaxies that were stripped of their outer layers after
colliding into other, still larger galaxies. Now, the same group
of astronomers has found two more ultra-compact dwarf galaxies
with super-massive black holes. Together, the three examples
suggest that black holes may lurk at the centres of most of such
objects, potentially doubling the number of super-massive black
holes known in the Universe. The black holes make up a high
percentage of the compact galaxies' total mass, supporting the
idea that the dwarfs are remnants of massive galaxies that were
ripped apart by larger galaxies. The team measured two ultra-
compact dwarf galaxies, named VUCD3 and M59cO, that orbit massive
galaxies in the Virgo galaxy cluster. They detected a super-
massive black hole in both galaxies; VUCD3's black hole has a
mass equivalent to 4.4 million Suns, making up about 13% of the
galaxy's total mass, and M59cO's black hole has a mass of 5.8
million Suns, making up about 18% of its total mass. For
comparison, the monstrous black hole at the centre of the Milky
Way has a mass of 4 million Suns, but makes up less than .01%
of our Galaxy's total mass.

To calculate the ultra-compact dwarf galaxies' mass, the
astronomers measured the movements of the stars with the Gemini
North telescope on Mauna Kea. They used adaptive optics to
reduce the distortions caused by the Earth's atmosphere. They
also analyzed images from the Hubble Space Telescope to measure
the distribution of the stars in each galaxy, and used computer
simulations to fit their observations. They found that the stars
at the centres of the galaxies moved much faster than those on
the outside, a classic signature of a black hole.


BRIDGE OF DARK-MATTER WEB IMAGED
RAS

Researchers at the University of Waterloo have been able to
capture the first composite image of a dark-matter bridge that
connects galaxies together. The composite image, which combines
a number of individual images, confirms predictions that galaxies
across the Universe are tied together through a cosmic web con-
nected by dark matter that has until now remained unobservable.
Dark matter, a mysterious substance that comprises around 25 per
cent of the Universe, does not shine, absorb or reflect light,
which has made it largely undetectable, except through gravity.
For decades, researchers have been predicting the existence of
dark-matter filaments between galaxies that act as a web-like
superstructure connecting galaxies together. The new image moves
us beyond predictions to something that we can see and measure.
As part of their research, astronomers used a technique called
weak gravitational lensing, an effect that causes the images of
distant galaxies to warp slightly under the influence of an
unseen mass such as a planet, a black hole, or in this case, dark
matter. The effect was measured in images from a multi-year sky
survey at the Canada-France-Hawaii Telescope. They combined
lensing images from more than 23,000 galaxy pairs located 4.5
billion light-years away to create a composite image or map that
shows the presence of dark matter between the pairs of galaxies.
Results show the dark-matter filament bridge is strongest between
systems less than 40 million light-years apart. By using that
technique, researchers are not only able to see that the dark-
matter filaments in the Universe exist, but are also able to see
the extent to which the filaments connect galaxies together.


COLD SPOT MAY INDICATE ANOTHER UNIVERSE
RAS

A super-void is unlikely to explain a 'Cold Spot' in the cosmic
microwave background, according to the results of a new survey,
leaving room for exotic explanations like a collision between
universes, according to researchers from Durham University's
Centre for Extragalactic Astronomy. The cosmic microwave
background (CMB), a relic of the Big Bang, covers the whole sky.
At a temperature of 2.73 degrees above absolute zero (or -270.43
degrees C), the CMB has some anomalies, including the Cold Spot.
That feature, about 0.00015 degrees colder than its surroundings,
was previously claimed to be caused by a huge void, millions of
light-years across, containing relatively few galaxies. The
accelerating expansion of the Universe causes voids to leave
subtle redshifts on light as it passes through, owing to the
'integrated Sachs-Wolfe effect'. In the case of the CMB that is
observed as cold imprints. It was proposed that a very large
foreground void could, in part, imprint the CMB Cold Spot which
has been a source of tension in models of standard cosmology.
Previously, most searches for a super-void connected with the
Cold Spot have estimated distances to galaxies from their
colours. With the expansion of the Universe, galaxies have their
light redddened by the cosmological redshift. The more distant
the galaxy is, the higher its observed redshift. By measuring
the colours of galaxies, their redshifts, and thus their
distances, can be estimated, though with a high degree of
uncertainty.

In the new work, the Durham team presents the results of a
comprehensive survey of the redshifts of 7,000 galaxies,
harvested 300 at a time with a spectrograph deployed on the
Anglo-Australian Telescope. From that data set, the team sees no
evidence of a super-void capable of explaining the Cold Spot
within the standard theory. The researchers instead found that
the Cold Spot region, previously thought to be under-populated
with galaxies, is split into smaller voids, surrounded by
clusters of galaxies. That 'soap-bubble' structure is much like
the rest of the Universe, illustrated by the visual similarity
between the galaxy distributions in the Cold Spot area and a
control field elsewhere. The voids cannot explain the Cold Spot
under standard cosmology. There is a possibility that some non-
standard model could be proposed to link the two in the future,
but the data place powerful constraints on any attempt to do
that. If there really is no super-void that can explain the Cold
Spot, simulations of the standard model of the Universe give odds
of 1 in 50 that the Cold Spot arose by chance. That means that
we can not rule out the possibility that the Spot is caused by a
statistical fluctuation explicable by the standard model. But if
that is not the answer, then there are more exotic explanations.
Perhaps the most extreme of those is that the Cold Spot was
caused by a collision between our Universe and another 'bubble
Universe'. If further, more detailed, analysis of CMB data were
to prove that to be the case, then the Cold Spot might be taken
as the first evidence for the multiverse -- and millions of other
universes like our own might exist. But that is rather 'building
castles in the air': for the moment, the most that can safely be
said is that the lack of a super-void to explain the Cold Spot
has tilted the balance towards more unusual explanations, ideas
that will need to be tested by more detailed observations of the
CMB.


Bulletin compiled by Clive Down

(c) 2017 The Society for Popular Astronomy

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Electronic News Bulletin No. 445 2017 May 21


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THIRD-LARGEST DWARF PLANET HAS MOON
NASA/Goddard Space Flight Center

The combined power of three space observatories, including the
Hubble Space Telescope, has helped astronomers discover a moon
orbiting the third-largest dwarf planet, catalogued as 2007 OR10.
The pair resides in the frigid outskirts of the Solar System
called the Kuiper Belt, a realm of icy debris left over from the
system's formation 4.6 billion years ago. With this discovery,
most of the known dwarf planets in the Kuiper Belt larger than
600 miles across have companions. Those bodies provide insight
into how moons formed in the young Solar System. The discovery
of satellites around all of the known large dwarf planets (except
for Sedna) means that, when those bodies formed, a very long time
ago, collisions must have been more frequent, and that is a
constraint on the formation models. If there were frequent
collisions, then it was quite easy to form satellites. The
objects most likely slammed into one another more often because
they inhabited a crowded region. But the speed of the colliding
objects could not have been too fast or too slow, according to
the astronomers. If the impact velocity were too great, the
smash-up would have created lots of debris that could have
escaped from the system; if too slow, the collision would have
produced only an impact crater.

The team discovered the moon in archival images of 2007 OR10
taken by Hubble's Wide-Field Camera 3. Observations taken of the
dwarf planet by the Kepler space telescope first tipped off the
astronomers to the possibility of a moon circling it. Kepler
revealed that 2007 OR10 has a slow rotation period of 45 hours.
Typical rotation periods for Kuiper-Belt Objects are under 24
hours. The team looked in the Hubble archive because the slower
rotation period could have been caused by the gravitational
effect of a moon. The initial investigator missed the moon in
the Hubble images because it is very faint. The astronomers
observed the moon in two separate Hubble observations spaced a
year apart. The images show that the moon is gravitationally
bound to 2007 OR10 because it moves with the dwarf planet, as
seen against a background of stars. However, the two observa-
tions did not provide enough information for the astronomers to
determine an orbit. They calculated the diameters of both
objects on the basis of observations in far-infrared light by
the Herschel Space Observatory, which measured their thermal
emission. The dwarf planet is about 950 miles across, and its
moon is estimated to be 150--250 miles in diameter. 2007 OR10,
like Pluto, follows an eccentric orbit, and is currently three
times farther from the Sun than Pluto is. 2007 OR10 is a member
of the exclusive club of 'dwarf planets', of which there are
nine. Of those bodies, only Pluto and Eris are larger.


'DETERGENT' MOLECULES MAY DRIVE METHANE CHANGES
NASA

A new study finds that recent increases in global methane levels
observed since 2007 are not necessarily due to increasing
emissions, but instead may be due to changes in how long methane
remains in the atmosphere after it is emitted. The second-most-
important human-produced greenhouse gas after carbon dioxide,
methane is colourless, odourless and can be hard to track. The
gas has a wide range of sources, from decomposing biological
material to leaks in natural-gas pipelines. In the early 2000s,
atmospheric scientists studying methane found that its global
concentration -- which had increased for decades, driven by
methane emissions from fossil fuels and agriculture -- levelled
off as the sources of methane reached a balance with its
destruction mechanisms. The methane levels remained stable for a
few years, then unexpectedly started rising again in 2007, a
trend that is still continuing. Previous studies of the renewed
increase have focused on high-latitude wetlands or fossil fuels,
Asian agricultural growth, or tropical wetlands as potential
sources of the increased emissions. But the new study suggests
that methane emissions might not have increased dramatically
since 2007 after all.

The researchers used long-term measurements of methane, its
isotopes and 1,1,1-trichloroethane (a compound that serves as a
proxy for estimating how long methane remains in the atmosphere)
from numerous global ground stations. From those data, the
scientists were able to determine sources of methane and how
quickly it is destroyed in the Earth's atmosphere. They found
that the most likely explanation for the recent increase has less
to do with methane emissions than previously thought and more to
do with changes in the availability of the hydroxyl radical (OH),
which breaks down methane in the atmosphere. The amount of
hydroxyl in the atmosphere has an impact on global methane
concentrations. If global levels of hydroxyl decrease, global
methane concentrations will increase -- even if methane emissions
remain constant. In tracking the observed changes in methane and
the inferred changes in hydroxyl, scientists noted that fluctua-
tions in hydroxyl concentrations can explain some of the recent
methane trends. However, the scientists cannot explain the
global changes in hydroxyl concentrations seen in the past
decade. They say that future independent studies are needed to
quantify year-to-year variations in the hydroxyl radical and
their potential drivers. They would also like to see the trends
they detected verified with more detailed studies of the sources
and the destruction mechanisms of methane, particularly in the
tropics.


A FAR-FLUNG MEMBER OF THE SOLAR SYSTEM
National Radio Astronomy Observatory

Using the Atacama Large Millimeter/submillimeter Array (ALMA),
astronomers have obtained extraordinary details about a recently
discovered far-flung member of the Solar System, the planetary
body 2014 UZ224, informally known as DeeDee. At about three
times the current distance of Pluto from the Sun, DeeDee is the
second-most-distant-known trans-Neptunian object (TNO) with a
confirmed orbit, surpassed only by the dwarf planet Eris.
Astronomers estimate that there are tens of thousands of such icy
bodies in the outer Solar System beyond the orbit of Neptune.
The new ALMA data reveal, for the first time, that DeeDee is
roughly 635 kilometres across, or about two-thirds the diameter
of Ceres, the largest member of the asteroid belt. At that size,
DeeDee should have enough mass to be spherical, the criterion
necessary for astronomers to consider it to be a dwarf planet,
though it has yet to receive that official designation.
Currently, DeeDee is about 92 astronomical units (AU) from the
Sun. It takes DeeDee more than 1,100 years to complete one
orbit; light from DeeDee takes nearly 13 hours to reach the
Earth.

The object was discovered with the 4-metre Blanco telescope at
the Cerro Tololo Inter-American Observatory in Chile as part of
ongoing observations for the 'Dark Energy Survey', that seeks to
understand the accelerating expansion of the Universe. The Dark
Energy Survey produces vast numbers of astronomical images, which
give astronomers the opportunity to search also for distant
Solar-System objects. The initial search, which includes nearly
15,000 images, identified more than a thousand million candidate
objects. The vast majority of them turned out to be background
stars and even-more-distant galaxies. A small fraction, however,
were observed to move slowly across the sky over successive
observations, the telltale sign of a TNO.

One such object was identified on 12 separate images. The
astronomers informally dubbed it DeeDee, which is short for
Distant Dwarf. The optical data from the Blanco telescope
enabled the astronomers to measure DeeDee's distance and orbital
properties, but they were unable to determine its size or other
physical characteristics. It was possible that DeeDee was a
relatively small member of the Solar System, yet reflective
enough to be detected. Alternatively, it could be uncommonly
large and dark, reflecting only a tiny portion of the feeble
sunlight that reaches it; both scenarios would produce identical
optical data. Since ALMA observes the cold, dark Universe, it is
able to detect the heat -- in the form of millimetre-wavelength
radiation -- emitted naturally by cold objects in space. The
heat signature from a distant Solar-System object would be
directly proportional to its size. By comparing the ALMA
observations to the earlier optical data, the astronomers had the
information necessary to calculate the object's size. Objects
like DeeDee are cosmic leftovers from the formation of the Solar
System. Their orbits and physical properties reveal important
details about the formation of planets, including the Earth.
This discovery shows that it is possible to detect very distant,
slowly moving objects in the Solar System. The researchers note
that the same technique might be used to detect the hypothesized
'Planet Nine' that may reside far beyond DeeDee and Eris.


STUDY SHOWS MOST HABITABLE PLANETS LACK DRY LAND
RAS

A new study has used a statistical model to suggest that most
habitable planets may be dominated by oceans spanning over 90% of
their surface area. The author of the study has constructed a
statistical model -- based on Bayesian probability -- to predict
the division between land and water on habitable exo-planets.
For a planetary surface to have extensive areas of both land and
water, a delicate balance must be struck between the volume of
water it retains over time, and how much space it has to store it
in its oceanic basins. Both of those quantities may vary
substantially across the full spectrum of water-bearing worlds,
and why the Earth's values are so well balanced is an unresolved
and long-standing conundrum. The model predicts that most
habitable planets will be dominated by oceans spanning over 90%
of their surface areas. That conclusion is reached because the
Earth itself is close to being a so-called 'water world' - a
world where all land is immersed under a single ocean. The new
work finds that the Earth's finely balanced oceans may be a
consequence of the 'anthropic principle' -- more often used in a
cosmological context -- which accounts for how our observations
of the Universe are influenced by the requirement for the
formation of sentient life. On the basis of the Earth's ocean
coverage of 71%, there is evidence supporting the hypothesis that
anthropic selection effects are at work.

To test the statistical model, feedback mechanisms were taken
into account, such as the deep-water cycle and erosion and
deposition processes. The study also proposes a statistical
approximation to determine the diminishing habitable land area
for planets with smaller oceans as they become increasingly
dominated by deserts. Why did we evolve on this planet and not
on one of the many other habitable worlds? In this study it is
suggested that the answer could be linked to a selection effect
involving the balance between land and water. Our understanding
of the development of life is far from complete, but it is not
quite so dire that we must adhere to the approximation that all
habitable planets have an equal chance of hosting intelligent
life.


SUPER-MASSIVE BLACK HOLES FOUND IN TINY GALAXIES
University of Utah

Three years ago, astronomers discovered that an ultra-compact
dwarf galaxy contained a super-massive black hole, then the
smallest known galaxy to harbour such a giant black hole. The
findings suggested that the dwarfs were probably tiny leftovers
of larger galaxies that were stripped of their outer layers after
colliding into other, still larger galaxies. Now, the same group
of astronomers has found two more ultra-compact dwarf galaxies
with super-massive black holes. Together, the three examples
suggest that black holes may lurk at the centres of most of such
objects, potentially doubling the number of super-massive black
holes known in the Universe. The black holes make up a high
percentage of the compact galaxies' total mass, supporting the
idea that the dwarfs are remnants of massive galaxies that were
ripped apart by larger galaxies. The team measured two ultra-
compact dwarf galaxies, named VUCD3 and M59cO, that orbit massive
galaxies in the Virgo galaxy cluster. They detected a super-
massive black hole in both galaxies; VUCD3's black hole has a
mass equivalent to 4.4 million Suns, making up about 13% of the
galaxy's total mass, and M59cO's black hole has a mass of 5.8
million Suns, making up about 18% of its total mass. For
comparison, the monstrous black hole at the centre of the Milky
Way has a mass of 4 million Suns, but makes up less than .01%
of our Galaxy's total mass.

To calculate the ultra-compact dwarf galaxies' mass, the
astronomers measured the movements of the stars with the Gemini
North telescope on Mauna Kea. They used adaptive optics to
reduce the distortions caused by the Earth's atmosphere. They
also analyzed images from the Hubble Space Telescope to measure
the distribution of the stars in each galaxy, and used computer
simulations to fit their observations. They found that the stars
at the centres of the galaxies moved much faster than those on
the outside, a classic signature of a black hole.


BRIDGE OF DARK-MATTER WEB IMAGED
RAS

Researchers at the University of Waterloo have been able to
capture the first composite image of a dark-matter bridge that
connects galaxies together. The composite image, which combines
a number of individual images, confirms predictions that galaxies
across the Universe are tied together through a cosmic web con-
nected by dark matter that has until now remained unobservable.
Dark matter, a mysterious substance that comprises around 25 per
cent of the Universe, does not shine, absorb or reflect light,
which has made it largely undetectable, except through gravity.
For decades, researchers have been predicting the existence of
dark-matter filaments between galaxies that act as a web-like
superstructure connecting galaxies together. The new image moves
us beyond predictions to something that we can see and measure.
As part of their research, astronomers used a technique called
weak gravitational lensing, an effect that causes the images of
distant galaxies to warp slightly under the influence of an
unseen mass such as a planet, a black hole, or in this case, dark
matter. The effect was measured in images from a multi-year sky
survey at the Canada-France-Hawaii Telescope. They combined
lensing images from more than 23,000 galaxy pairs located 4.5
billion light-years away to create a composite image or map that
shows the presence of dark matter between the pairs of galaxies.
Results show the dark-matter filament bridge is strongest between
systems less than 40 million light-years apart. By using that
technique, researchers are not only able to see that the dark-
matter filaments in the Universe exist, but are also able to see
the extent to which the filaments connect galaxies together.


COLD SPOT MAY INDICATE ANOTHER UNIVERSE
RAS

A super-void is unlikely to explain a 'Cold Spot' in the cosmic
microwave background, according to the results of a new survey,
leaving room for exotic explanations like a collision between
universes, according to researchers from Durham University's
Centre for Extragalactic Astronomy. The cosmic microwave
background (CMB), a relic of the Big Bang, covers the whole sky.
At a temperature of 2.73 degrees above absolute zero (or -270.43
degrees C), the CMB has some anomalies, including the Cold Spot.
That feature, about 0.00015 degrees colder than its surroundings,
was previously claimed to be caused by a huge void, millions of
light-years across, containing relatively few galaxies. The
accelerating expansion of the Universe causes voids to leave
subtle redshifts on light as it passes through, owing to the
'integrated Sachs-Wolfe effect'. In the case of the CMB that is
observed as cold imprints. It was proposed that a very large
foreground void could, in part, imprint the CMB Cold Spot which
has been a source of tension in models of standard cosmology.
Previously, most searches for a super-void connected with the
Cold Spot have estimated distances to galaxies from their
colours. With the expansion of the Universe, galaxies have their
light redddened by the cosmological redshift. The more distant
the galaxy is, the higher its observed redshift. By measuring
the colours of galaxies, their redshifts, and thus their
distances, can be estimated, though with a high degree of
uncertainty.

In the new work, the Durham team presents the results of a
comprehensive survey of the redshifts of 7,000 galaxies,
harvested 300 at a time with a spectrograph deployed on the
Anglo-Australian Telescope. From that data set, the team sees no
evidence of a super-void capable of explaining the Cold Spot
within the standard theory. The researchers instead found that
the Cold Spot region, previously thought to be under-populated
with galaxies, is split into smaller voids, surrounded by
clusters of galaxies. That 'soap-bubble' structure is much like
the rest of the Universe, illustrated by the visual similarity
between the galaxy distributions in the Cold Spot area and a
control field elsewhere. The voids cannot explain the Cold Spot
under standard cosmology. There is a possibility that some non-
standard model could be proposed to link the two in the future,
but the data place powerful constraints on any attempt to do
that. If there really is no super-void that can explain the Cold
Spot, simulations of the standard model of the Universe give odds
of 1 in 50 that the Cold Spot arose by chance. That means that
we can not rule out the possibility that the Spot is caused by a
statistical fluctuation explicable by the standard model. But if
that is not the answer, then there are more exotic explanations.
Perhaps the most extreme of those is that the Cold Spot was
caused by a collision between our Universe and another 'bubble
Universe'. If further, more detailed, analysis of CMB data were
to prove that to be the case, then the Cold Spot might be taken
as the first evidence for the multiverse -- and millions of other
universes like our own might exist. But that is rather 'building
castles in the air': for the moment, the most that can safely be
said is that the lack of a super-void to explain the Cold Spot
has tilted the balance towards more unusual explanations, ideas
that will need to be tested by more detailed observations of the
CMB.


ENB 444

Clive

CERES' TEMPORARY ATMOSPHERE LINKED TO SOLAR ACTIVITY
NASA

Scientists have long thought that Ceres, the largest object in the
asteroid belt and now classified as a 'dwarf planet', may have a very
weak, transient atmosphere, but uncertainties have lingered about its
origin and why it is not always present. Now, researchers suggest
that the temporary atmosphere is related to the behaviour of the Sun,
rather than Ceres' proximity to the Sun. The study was conducted by
scientists from the Dawn mission and others who previously identified
water vapour on Ceres. When energetic particles from the Sun hit ice
on or near the surface of Ceres, they transfer energy to the water
molecules as they collide. That frees the water molecules from the
ground, allowing them to escape and create a tenuous atmosphere that
may last for a week or so. The results also have implications for
other airless, water-rich bodies of the Solar System, including the
polar regions of the Moon and some asteroids. Atmospheric releases
might be expected from their surfaces, too, when solar activity
occurs. Before Dawn arrived in orbit round Ceres in 2015, evidence
for an atmosphere had been detected by some observatories at certain
times, but not at others, suggesting that it is a transient
phenomenon. The IUE satellite detected hydroxyl emission from Ceres
in 1991, but not in 1990. Then, in 2007, ESO's VLT searched for a
hydroxide emission, but did not find any. ESA's Herschel observatory
detected water in the possible weak atmosphere, or 'exosphere', of
Ceres on three occasions, but did not on a fourth attempt.

As Dawn began its study of Ceres in 2015 March, scientists found ample
evidence for water in the form of ice. The spacecraft's gamma-ray and
neutron detector (GRaND) found that the surface is rich in hydrogen,
which is consistent with broad expanses of water ice. The ice is
nearer to the surface at higher latitudes, where temperatures are
lower. Ice has been detected directly in the small bright crater
called Oxo and in at least one of the craters that are persistently in
shadow in the northern hemisphere. Other research has suggested that
persistently shadowed craters are likely to harbour ice. Addition-
ally, the shapes of craters and other features are consistent with
significant water-ice content in the crust. Because of that evidence
for abundant ice, many scientists think that Ceres' exosphere is
created in a process similar to the one that occurs on comets, even
though they are much smaller. In that model, the closer Ceres gets to
the Sun, the more water vapour is released because of ice sublimating
near or at the surface. But the new study suggests comet-like
behaviour may not explain the mix of detections and non-detections of
a weak atmosphere. Scientists showed that past detections of the
transient atmosphere coincided with higher concentrations of energetic
protons from the Sun. Non-detections coincided with lower concen-
trations of such particles. Also, the best detections of Ceres'
atmosphere did not occur at its closest approach to the Sun. That
suggests that solar activity, rather than Ceres' proximity to the Sun,
is a more important factor in generating an exosphere. GRaND data
suggested that, during a six-day period in 2015, Ceres accelerated
electrons from the solar wind to very high energies. In its orbital
path, Ceres is currently getting closer to the Sun. But the Sun is
now in a particularly quiet period, expected to last for several more
years. Since their results indicate Ceres' exosphere is related to
solar activity, study authors are predicting that the dwarf planet
will have little to no atmosphere for some time. However, they
recommend that other observatories monitor Ceres for future emissions.


ATMOSPHERE AROUND EARTH-LIKE PLANET
Keele University

Astronomers have detected an atmosphere around the super-Earth planet
GJ 1132b. That marks the first detection of an atmosphere around an
Earth-like planet other than the Earth itself, and thus is a
significant step on the path towards the detection of life outside
the Solar System. Astronomers' current strategy for finding life on
another planet is to detect the chemical composition of that planet's
atmosphere, on the look-out for chemical imbalances which could be
caused by living organisms. In the case of our own Earth, the
presence of large amounts of oxygen is a tell-tale sign of life.
Until these findings, the only previous detections of exo-planet
atmospheres all involved gas giants reminiscent of a high-temperature
Jupiter. GJ 1132b is significantly hotter and a bit larger than the
Earth, so one possibility is that it is a 'water world' with an
atmosphere of hot steam.

The planet GJ 1132b orbits the low-mass star GJ 1132 in the southern
constellation Vela, 39 light-years away. The team used the GROND
imager at the 2.2-m ESO telescope in Chile to observe the planet
simultaneously at seven different wavelength bands spanning the
optical and near-infrared. As GJ 1132b is a transiting planet, it
passes directly between the Earth and its host star every 1.6 days,
blocking a small fraction of the star's light. From the amount of
light lost, astronomers can deduce the planet's size -- in this case
1.4 times that of the Earth. The new observations showed the planet
to be larger in one of the seven wavelength bands. That suggests the
presence of an atmosphere that is opaque at that specific wavelength
(making the planet appear larger), but transparent at all the others.
The discovery of that atmosphere is encouraging. Very-low-mass stars
are extremely common (much more so than Sun-like stars), and are known
to host lots of small planets. But they also show a lot of magnetic
activity, causing high levels of X-rays and ultraviolet light to be
produced, which might completely evaporate the planets' atmospheres.
However, the properties of GJ 1132b show that an atmosphere can endure
that for millions of years without being destroyed. In view of the
huge number of very-low-mass stars and planets, that might imply that
the conditions suitable for life are common in the Universe.


STELLAR FIREWORKS OF STAR BIRTH
ESO

1350 light-years away, in the constellation Orion, lies a dense and
active star-formation factory called Orion Molecular Cloud 1 (OMC-1),
part of the same complex as the famous Orion Nebula. Stars are born
when a cloud of gas hundreds of times the mass of the Sun begins to
collapse under its own gravity. In the densest regions, proto-stars
ignite and begin to drift about randomly. Over time, some stars begin
to fall toward a common centre of gravity, which is usually dominated
by a particularly large proto-star -- and if the stars have a close
encounter before they can escape their stellar nursery, violent
interactions can occur. About 100,000 years ago, several proto-stars
started to form deep within OMC-1. Gravity began to pull them
together with ever-increasing speed, until 500 years ago two of them
finally clashed. Astronomers are not sure whether they merely grazed
each other or collided head-on, but either way it triggered a powerful
eruption that launched other nearby proto-stars and hundreds of
colossal streamers of gas and dust out into inter-stellar space at
over 150 km/s. That cataclysmic interaction released as much energy
as the Sun emits in 10 million years. Fast forward 500 years, and a
team of astronomers has used the Atacama array of radio telescopes
(ALMA) to observe the heart of the cloud. There they found the
flung-out debris from the explosive birth of that clump of massive
stars, looking like a cosmic version of fireworks with giant streamers
rocketing off in all directions.

Such explosions are expected to be relatively short-lived, the
remnants like those seen by ALMA lasting only centuries. But although
they are fleeting, such proto-stellar explosions may be relatively
common. By destroying their parent cloud, such events might also help
to regulate the pace of star formation in giant molecular clouds.
Hints of the explosive nature of the debris in OMC-1 were first
revealed by the 'Submillimeter Array' in Hawaii in 2009. The team
also observed the object in the near-infrared with the Gemini South
telescope in Chile, revealing the remarkable structure of the
streamers, which extend nearly a light-year from end to end. The new
ALMA images, however, show the explosive nature in high resolution,
unveiling important details about the distribution and high-velocity
motion of the carbon monoxide (CO) gas inside the streamers. That may
help astronomers understand what impact such events could have on star
formation across the galaxy.


GRAVITATIONAL WAVE KICKS OUT BLACK HOLE
Space Telescope Science Institute (STScI)

Astronomers have uncovered a super-massive black hole that may have
been propelled out of the centre of a distant galaxy by gravitational
waves. Though there have been several other suspected, similarly
booted, black holes elsewhere, none has been confirmed so far.
Astronomers think that the object, detected by the HST, is a very
strong case. With a mass of more than 1 billion suns, it is the
most massive black hole ever detected to have been kicked out of its
central home. Researchers estimate that it took energy equivalent to
100 million supernovae exploding simultaneously to jettison the black
hole. The most plausible explanation for such propulsive energy is
that the object was given a kick by gravitational waves unleashed by
the merger of two hefty black holes at the centre of the host galaxy.
First predicted by Einstein, gravitational waves are ripples in space
that are created when two massive objects collide. The ripples are
similar to the concentric circles produced when a rock is thrown into
a pond. Last year, the Laser Interferometer Gravitational-Wave
Observatory (LIGO) proved that gravitational waves exist by detecting
them emanating from the union of two black holes which were several
times more massive than the Sun.

Hubble images taken in visible and near-infrared light provided the
first clue that the galaxy was unusual. The images revealed a bright
quasar, the energetic signature of a black hole, far from the galactic
core. Black holes cannot be observed directly, but they are the
energy source at the heart of quasars -- intense, compact sources of
radiation that can outshine an entire galaxy. The quasar, named
3C 186, and its host galaxy are 8 billion light-years away in a
galaxy cluster. The team discovered the galaxy's peculiar features
while conducting a Hubble survey of distant galaxies unleashing
powerful blasts of radiation in the throes of galaxy mergers. The
team calculated the black hole's distance from the core by comparing
the distribution of starlight in the host galaxy with that of a normal
elliptical galaxy from a computer model. The black hole had travelled
more than 35,000 light-years from the centre, which is more than the
distance between the Sun and the centre of the Milky Way. On the
basis of spectroscopic observations taken by Hubble and the Sloan
survey, the researchers estimated the black hole's mass and measured
the speed of gas trapped near it. They found that the gas around the
black hole was flying away from the galaxy's centre at 4.7 million
miles an hour. That measurement is also a gauge of the black hole's
velocity, because the gas is gravitationally locked to the hole. At
that speed an object would travel from the Earth to the Moon in three
minutes! That is fast enough for the black hole to escape from the
galaxy in 20 million years and roam through the Universe forever.
The researchers are lucky to have caught the event, because not every
black-hole merger produces imbalanced gravitational waves that propel
a black hole in the opposite direction.


EXPLAINING EXPANSION OF UNIVERSE WITHOUT DARK ENERGY
RAS

Enigmatic dark energy, despite being thought by some people to make up
68% of the Universe, may not exist at all, according to a Hungarian--
American team. The researchers believe that standard models of the
Universe fail to take account of its changing structure, but that once
that is done the need for dark energy disappears. Our Universe was
formed in the Big Bang, 13.8 billion years ago, and has been
expanding ever since. The key piece of evidence for the expansion is
Hubble's 'law', that the speed with which a galaxy moves away from us
is proportional to its distance. From the 1920s, mapping the
velocities of galaxies led scientists to conclude that the whole
Universe is expanding, and that it began as a vanishingly small point.
In the second half of the twentieth century, astronomers found
evidence for unseen ('dark') matter by observing that something extra
was needed to explain the motion of stars within galaxies. Dark
matter is now thought by some to make up 27% of the content of
Universe (in contrast, 'ordinary' matter amounts to only 5%).
Observations in the 1990s of the explosions of white dwarf stars in
binary systems, so-called Type Ia supernovae, then led scientists to
the conclusion that a third component, dark energy, made up 68% of the
cosmos, and is responsible for driving an acceleration in the
expansion of the Universe.

In the new work, the researchers question the existence of dark energy
and suggest an alternative explanation. They argue that conventional
cosmology relies on approximations that ignore the Universe's
structure and in which matter is assumed to have a uniform density.
Einstein's equations of general relativity that describe the expansion
of the Universe are so complex mathematically that for a hundred years
no solutions accounting for the effect of cosmic structures have been
found. We know from very precise supernova observations that the
Universe is accelerating, but at the same time we rely on coarse
approximations to Einstein's equations which may introduce serious
side-effects, such as the need for dark energy, in the models designed
to fit the observational data. In practice, normal and dark matter
appear to fill the Universe with a foam-like structure, where galaxies
are located on the thin walls between bubbles, and are grouped into
super-clusters. The insides of the bubbles are, in contrast, almost
empty of both kinds of matter. Using a computer simulation to model
the effect of gravity on the distribution of millions of particles of
dark matter, the scientists reconstructed the evolution of the
Universe, including the early clumping of matter and the formation of
large-scale structure. Unlike conventional simulations with a
smoothly expanding Universe, taking the structure into account led to
a model where different regions of the cosmos expand at different
rates. The average expansion rate, though, is consistent with present
observations, which suggest an overall acceleration. The theory of
general relativity is fundamental to understanding the way the
Universe evolves. We do not question its validity; we question the
validity of the approximate solutions. The findings rely on a
mathematical conjecture which permits the differential expansion of
space, consistent with general relativity, and they show how the
formation of complex structures of matter affects the expansion.
Those issues were previously swept under the rug but taking them into
account can explain the acceleration without the need for dark energy.
If that finding is upheld, it could have a significant impact on
models of the Universe and the direction of research in physics.
For the past 20 years, astronomers and theoretical physicists have
speculated on the nature of dark energy, but it remains an unsolved
problem. With the new model, the team expects at the very least to
start a debate.


RETHINKING THE 'LITTLE ICE AGE'
RAS

A group of solar and climate scientists argues that the whole concept
of the 'Little Ice Age' is misleading, as the changes were small-
scale, seasonal and insignificant compared with present-day global
warming. Explanations for the cooling to the Earth's climate,
thought to have occurred between the 16th and 19th centuries, include
low solar activity, volcanic eruptions, human changes to land use and
natural climatological change. But researchers note that the
temperature shift was smaller than that seen in recent decades
resulting from the emission of greenhouse gases, and that although low
solar activity may have been one driving factor, it certainly was not
the only one. Researchers scrutinised historical records, such as the
accounts of 'frost fairs' when the River Thames froze solid, and
looked at the paintings from the era, such as the landscapes of Pieter
Bruegel the Elder, with 'Hunters in the Snow' depicting a cold winter
scene. Both of those are cited in support of the Little Ice Age
concept. From around 1650 to 1710, and to a lesser extent from 1790
to 1825, periods respectively known as the Maunder and Dalton Minima,
sunspot numbers were unusually low, an indication that the surface of
the Sun was slightly cooler. That external influence is often
suggested as an explanation for the colder conditions. Scientists
looked at the various pieces of evidence in more detail. They
compared direct temperature records and proxy data such as ice
records, with the years when the Thames was frozen over (whether or
not a frost fair took place), and with the indications of solar
activity. Historical climate change is assessed through a variety of
means. The Central England Temperature (CET) data set tracks
temperature from 1659, making it the oldest and longest-running
meteorological instrumental data sequence in the world. That direct
record is supplemented by studies of biological proxies such as tree
rings, corals, insect numbers and molluscs, all sensitive to climate
change.

The authors draw comparisons with the ice ages proper. Cores taken
from Antarctic ice allow global temperatures to be inferred, by
measuring the proportions of deuterium and of the oxygen isotope 18O,
compared with their lighter (normal) counterparts. It takes more
energy to evaporate water with a higher proportion of the heavier
atoms, and they are more easily lost from rainfall, before they are
deposited in ice found nearer the poles. The changing proportions of
those atoms allows researchers to assess how the temperature has
changed over millions of years. From those comparisons, the
scientists argue that the description of the period as an Ice Age is
misleading, as temperatures in that period fell far less than in a
glaciation. During the Little Ice Age (LIA), the average temperature
in the northern hemisphere fell by around 0.5 degrees. In contrast, in
the most recent major glaciation that came to an end around 12,000
years ago, global temperatures were typically 8°C colder than today.
Frost fairs also seem to be a poor indication of overall climate, as
they often did not take place despite the Thames freezing, partly for
many reasons, including puritanical authorities, or safety, as lives
were lost when the ice melted. The ending of the frost fairs had
nothing to do with climate change or solar activity, instead being
due to the increased river flow when the original London Bridge was
demolished in 1825, and the first Victoria embankment opened in 1870.
Both of those prevented the river from freezing completely, despite
many subsequent cold winters. Selective use of art-historical
evidence appears to reinforce the illusion of a prolonged cold spell.
Yet 'Hunters in the Snow', depicting a January scene, is part of a
series by Bruegel known as 'The Twelve Months'. Seven of the
paintings may have been lost, but those of February, July and November
all give no indication of unusually cold conditions. Consistently
with that, the team notes that even at the height of the LIA period,
colder European winters were still accompanied by many warm summers.
For example, 1701 is close to the lowest point of the Little Ice Age,
yet in both Paris and London the summer was reported as being
unbearably hot and the CET for July that year is the tenth-hottest
on record, with average temperatures for the month reaching 18.3°C.
The year 1676 is the second-hottest June on record at 18.0°C, yet it
too was in the middle of a run of cold winters. Such high summer
temperatures do not fit at all with the name 'Little Ice Age'. Much
more dramatic variations can result from large volcanic eruptions.
Samalas, a volcano which erupted in 1257 in what is now Indonesia,
ejected large amounts of dust into the atmosphere, causing a temporary
cooling effect. The years between 1570 and 1730, corresponding to the
coldest part of the LIA, also saw continuous lower-level volcanic
activity that may have suppressed temperatures. Volcanic eruptions
undoubtedly cause both cold winters and cold summers. One of the
clearest examples was the Tambora eruption of 1815 July, which caused
the next year to be called the year without a summer.


CASSINI MISSION PREPARES FOR GRAND FINALE
NASA

The Cassini spacecraft, in orbit around Saturn since 2004, is about
to begin the final chapter of its remarkable story. On April 26
the spacecraft will make the first of a series of dives through the
2,400-km gap between Saturn and its rings as part of the mission's
grand finale. During its time at Saturn, Cassini has made numerous
dramatic discoveries, including a global ocean that shows indications
of hydrothermal activity within the icy moon Enceladus, and liquid
methane seas on its moon Titan. Now, 20 years since launch and after
13 years orbiting Saturn, Cassini is running low on fuel. In 2010,
NASA decided to end the mission with a purposeful plunge into Saturn
this year in order to protect and preserve the planet's moons for
future exploration -- especially the potentially habitable Enceladus.
But the beginning of the end for Cassini is, in many ways, like a
whole new mission. Using expertise gained during the mission, Cassini
engineers designed a flight plan that will maximize the scientific
value of sending the spacecraft on its plunge into the planet on
September 15. As it ticks off its terminal orbits during the next
five months, the mission is expected to rack up an impressive list of
scientific achievements.

The mission team hopes to gain insights into the planet's internal
structure and the origins of the rings, obtain the first-ever sampling
of Saturn's atmosphere and particles coming from the main rings, and
capture the closest-ever views of Saturn's clouds and inner rings.
Cassini will begin its grand-finale orbits, with a last close fly-by
of the giant moon Titan, on April 22. As it has done many times over
the course of the mission, Titan's gravity will affect Cassini's
flight path. Cassini's orbit then will shrink so that instead of
making its closest approach to Saturn just outside the rings, it will
begin passing between the planet and the inner edge of its rings.
Astronomers expect the gap to be clear of particles large enough to
damage the spacecraft. In mid-September, following a distant
encounter with Titan, the spacecraft's path will be altered so that
it dives into the planet. When Cassini makes its final plunge into
Saturn's atmosphere, it will send data from several instruments --
most notably, data on the atmosphere's composition -- until its signal
is lost.

ENB 443

Clive

LESS RADIATION IN VAN ALLEN BELT WAS THAN BELIEVED
DOE/Los Alamos National Laboratory

Observations from NASA's Van Allen probes show that the fastest, most
energetic electrons in the inner radiation belt are actually much
rarer than scientists expected. That is good news for spacecraft that
are orbiting in the region and can be damaged by high levels of
radiation. The results will also help scientists to understand better
-- and detect -- effects from high-altitude nuclear explosions. The
Van Allen belts are two doughnut-shaped regions of charged particles
encircling the Earth. Past space missions have not been able to
distinguish electrons from high-energy protons in the inner radiation
belt. But by using a special instrument, the 'Magnetic Electron and
Ion Spectrometer' (MagEIS), on the Van Allen probes, scientists could
look at the particles separately for the first time. What they found
was surprising: almost none of the super-fast electrons -- the
relativistic electrons -- is present in the inner belt. Scientists
have long understood that, of the two radiation belts, the outer belt
is the more active one. During intense geomagnetic storms, when
charged particles from the Sun hurtle across the Solar System, the
outer radiation belt pulsates dramatically, growing and shrinking in
response to the pressure of the solar particles and magnetic field.
Scientists thought that the inner belt maintains a steady position
above the Earth's surface. The new results, however, show that that
is not always true. For example, during a very strong geomagnetic
storm in 2015 June, relativistic electrons were pushed deep into the
inner belt.

Given the rarity of the storms that can inject relativistic electrons
into the inner belt, the scientists now understand that lower levels
of radiation are typical there, a result that has implications for
spacecraft operating in that region. Knowing exactly how much and
what type of radiation is present in any given region of space may
enable scientists and engineers to design lighter and cheaper
satellites tailored to withstand the specific radiation levels they
are liable to encounter. That opens the possibility of doing science
that previously was not possible. For example, we can now investigate
under what circumstances the electrons penetrate the inner region and
see if more intense geomagnetic storms give electron showers that are
more intense or more energetic.


MANY FACES OF COMET 67P
NASA

Images returned from ESA's Rosetta mission indicate that during its
most recent trip through the inner Solar System, the surface of comet
67P/Churyumov-Gerasimenko was a very active place -- full of growing
fractures, collapsing cliffs and massive rolling boulders. Moving
material buried some features on the comet's surface while exhuming
others. As comets approach the Sun, they undergo spectacular changes
on their surfaces. That is something that we were not able really to
appreciate before the Rosetta mission, which gave us the chance to
look at a comet in ultra-high resolution for more than two years.
Most comets orbit the Sun in highly eccentric orbits that cause them
to spend most of their time in the extremely cold outer Solar System.
When a comet approaches the inner Solar System, the Sun begins to warm
the ice on and near the comet's surface. When the ice warms enough it
can rapidly sublimate (turn directly from the solid to the vapour
state). The sublimation process can occur with variable degrees of
intensity and time-scales and cause the surface to change rapidly.
Between 2014 August and 2016 September, Rosetta orbited comet 67P
during the comet's traverse of the inner Solar System. (That was
about a third of the comet's 'year': its orbital period is about 6.45
years.)

Scientists saw a massive cliff collapse and a large crack in the
'neck' of the comet get bigger and bigger. They discovered that a
huge 30-metre boulder had moved 140 metres from its original position
on the comet's nucleus. The massive rock probably moved as a result
of several outburst events that were detected close to its original
position. The warming of 67P also caused the comet's rotation rate to
speed up. The comet's increasing spin rate in the lead-up to
perihelion is thought to be responsible for a 500-metre-long fracture
observed in 2014 August that runs through the comet's neck. The
fracture was found to have increased in width by about 30 metres (100
feet) by 2014 December. Furthermore, in images taken in 2016 June, a
new 150- to 300-metre fracture was identified parallel to the original
one. The crack was extending -- indicating that the comet may split
up one day. Understanding how comets change and evolve with time may
give us important insights into the types and abundance of ices in
comets, and how long comets can stay in the inner Solar System before
losing all their ice and becoming balls of dust. That should helps us
understand better the conditions of the early Solar System, and
possibly even how life started.


PUREST, MOST MASSIVE BROWN DWARF
RAS

Astronomers have identified a record-breaking brown dwarf (a star too
small for nuclear fusion) with the 'purest' composition and the highest
mass yet known. The object, known as SDSS J0104+1535, is a member of
the 'halo' -- the outermost reaches -- of our Galaxy, made up of the
most ancient stars. Brown dwarfs are intermediate between planets and
fully-fledged stars. Their masses are too small for full nuclear
fusion of hydrogen to helium (with a consequent release of energy) to
take place, but they are usually significantly more massive than
planets. Located 750 light-years away in the constellation Pisces,
SDSS J0104+1535 is made of gas that is around 250 times purer than the
Sun -- it consists of more than 99.99% hydrogen and helium. It is
estimated to have formed about 10 (US-)billion years ago; measurements
suggest that it has a mass equivalent to 90 times that of Jupiter,
making it the most massive brown dwarf found to date. It was
previously not known if brown dwarfs could form from such primordial
gas, and the discovery points the way to a larger undiscovered
population of extremely pure brown dwarfs from our Galaxy's ancient
past. SDSS J0104+1535 has been classified as an L-type ultra-subdwarf
from its optical and near-infrared spectrum, observed with ESO's VLT.


CLUES ABOUT MISSING GALAXIES
RAS

Astronomers have developed a way to detect the ultraviolet (UV)
background of the Universe, which could help explain why there are so
few small galaxies in the cosmos. UV radiation is invisible but shows
up as visible red light when it interacts with gas. Researchers have
now found a way to measure it using instruments on Earth. The method
can be used to measure the evolution of the UV background through
cosmic time, mapping how and when it suppresses the formation of small
galaxies. The study could also help to produce more accurate computer
simulations of the evolution of the Universe. UV radiation is found
throughout the Universe and strips smaller galaxies of the gas that
forms stars, effectively stunting their growth. It is believed to be
the reason why some larger galaxies like our Milky Way do not have
many smaller companion galaxies. Simulations show that there should
be more small galaxies in the Universe, but UV radiation essentially
stopped them from developing by depriving them of the gas that they
need to form stars. Larger galaxies like the Milky Way were able to
withstand the cosmic blast because of the thick gas clouds surrounding
them. Massive stars and supermassive black holes produce huge amounts
of ultraviolet radiation, and their combined radiation builds up the
ultraviolet background. The UV radiation excites the gas in the
Universe, causing it to emit red (H-alpha) light in a somewhat similar
way to that in which the gas in a fluorescent tube is excited. The
research means that we can now measure and map the UV radiation, which
should help us to refine models of galaxy formation.

Researchers pointed the Multi-Unit Spectroscopic Explorer (MUSE), an
instrument on ESO's VLT in Chile, at the galaxy UGC 7321, which is 30
million light-years away. MUSE provides a spectrum for each pixel in
the image, allowing the researchers to map the red light produced by
the UV radiation illuminating the gas in that galaxy. The research
could also help scientists predict the temperature of the cosmic gas
with more accuracy. Ultraviolet radiation heats the cosmic gas to
temperatures higher than that of the surface of the Sun. Such hot gas
will not cool to make stars in small galaxies. That explains why
there are so few small galaxies in the Universe, and also why our
Milky Way has so few small satellite galaxies.


FIVE NEW SUB-ATOMIC PARTICLES FOUND
BBC News

The Large Hadron Collider has discovered new sub-atomic particles that
could help to explain how the centres of atoms are held together. The
particles are all different forms of the so-called Omega-c baryon,
whose existence was confirmed in 1994. Physicists had always believed
that various types existed but had not been able to detect them until
now. The discovery will shed light on the operation of the 'strong
force', which glues the insides of atoms. The centres of atoms
consist of neutrons and protons. They in turn are made up of smaller
particles called quarks, which have unusual names. Those inside
neutrons and protons are called 'Up' and 'Down'. The quarks are held
together by the nuclear 'strong force'. Physicists have a theory
called quantum chromodynamics for how the nuclear strong force works,
but using it to make predictions requires very complex calculations.
The Omega-c baryon is in the same family of particles as the neutron
and proton, but it can be thought of as a more exotic cousin. It too
is made up of quarks but they are called 'Charm' and 'Strange', and
they are heavier versions of the Up and Down quarks. Since the
Omega-c particle's discovery, it was thought that there were heavier
versions -- its bigger brothers and sisters if you like. Now,
physicists at the European Organization for Nuclear Research (CERN)
have found them. They believe that, by studying those siblings, they
will learn more about the workings of the nuclear strong force. The
discovery will shed light on how quarks bind together. It may have
implications not only to understand protons and neutrons better, but
also more exotic multi-quark states, such as tetraquarks and
pentaquarks.


AROMATIC MOLECULES IN EARLY UNIVERSE
University of California - Riverside

Molecules found in car-engine exhaust fumes, that are thought to have
contributed to the origin of life on Earth, have made astronomers
seriously to underestimate the number of stars that were forming in
the early Universe. The molecules are called polycyclic aromatic
hydrocarbons (PAH); they constitute a set that has more than a hndred
members. On the Earth occur naturally in coal and tar; in space, they
are a component of the dust, which along with gas, fills the space
between stars within galaxies. The study represents the first time
that astronomers have been able to measure variations of PAH emissions
in distant galaxies with different properties. It has important
implications for the studies of distant galaxies because absorption
and emission of energy by dust particles can change astronomers' views
of distant galaxies. The research was conducted as part of the
University of California-based MOSDEF survey, a study that uses the
Keck telescope in Hawaii to observe the content of about 1500 galaxies
seen as they were when the Universe was 1.5 to 4.5 billion years old.
The researchers observed the emitted visible-light spectra of a large
and representative sample of galaxies during the peak era of star-
formation activity in the Universe. In addition, the researchers
incorporated infrared imaging data from the Spitzer and Herschel space
observatories to trace the polycyclic aromatic hydrocarbon emission in
mid-infrared bands and the thermal dust emission in far-infrared
wavelengths.

The researchers concluded that the emission of polycyclic aromatic
hydrocarbon molecules is suppressed in low-mass galaxies, which also
have a lower abundance of metals, by which they mean all atoms heavier
than hydrogen and helium. Those results indicate that the polycyclic
aromatic hydrocarbon molecules are likely to be destroyed in the
hostile environment of low-mass and metal-poor galaxies with intense
radiation. The researchers also found that the polycyclic aromatic
hydrocarbon emission is relatively weaker in young galaxies in
comparison with older ones, which may be because the relevant
molecules are not produced in large quantities in young galaxies.
They found that the star-formation activity and infrared luminosity in
the universe 10 billion years ago was approximately 30 per cent higher
than previous figures indicated. Studying the properties of the
polycyclic aromatic hydrocarbon mid-infrared emission bands in the
distant Universe is of fundamental importance to improving our
understanding of the evolution of dust and chemical enrichment in
galaxies throughout cosmic time. That will be one of the tasks of the
James Webb space telescope when it is launched next year.

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Clive

CANADIAN FOSSILS ARE OLDEST EVIDENCE OF LIFE
Live Science

Fossil microbes almost 4.3 Canadian-billion years old that have been
found in Canada are similar to the bacteria that thrive today around
sea-floor hydrothermal vents and may represent the oldest known
evidence of life on Earth. Researchers said that the fossils, from
the Hudson Bay shoreline in northern Quebec near the Nastapoka
Islands, lend credence to the hypothesis that hydrothermal vents
spewing hot water may have been the cradle of life on Earth relatively
soon after the planet formed. They also said that they thought that
at that time Mars had oceans, long since gone, that may have boasted
similar conditions conducive to the advent of life. Tiny filaments
and tubes made of iron oxide, formed by the microbes, were found
encased in layers of quartz that experts have determined to be between
3.7 and 4.28 billion years old, according to the study published in the
'Nature'. The researchers expressed confidence that the fossils were
formed by organisms, saying no non-biological explanation was plausible.

It was primordial microbes like those described in the study that set
in motion the evolutionary march toward complex life and, eventually,
the appearance of humans 200,000 years ago. The scientists said that
the primordial microbes' structure closely resembled modern bacteria
that dwell near iron-rich hydrothermal vents. They believe that, like
their modern counterparts, they were iron-eaters. The rock's compo-
sition was consistent with a deep-sea vent environment. The Earth
formed about 4.5 billion years ago and the oceans appeared about 100
million years later. If the fossils are indeed 4.28 billion years old, that would
suggest an almost instantaneous emergence of life after ocean formation.
The fossils appear to be older than any other previously discovered
evidence of life. For example, other scientists last year described 3.7
billion-year-old fossilized microbial mats, called stromatolites, from
Greenland.


WATER-RICH HISTORY OF MARS --- NEW EVIDENCE
DOE/Lawrence Berkeley National Laboratory

Mars may have been a wetter place than previously thought, according
to research on simulated Martian meteorites. Researchers found
evidence that a mineral found in Martian meteorites -- which had been
considered as proof of an ancient dry environment on Mars -- may have
originally been a hydrogen-containing mineral that could indicate a
more water-rich history for the Red Planet. An international research
team in the study, created a synthetic version of a hydrogen-
containing mineral known as whitlockite. After shock-compression
experiments on whitlockite samples that simulated the conditions of
ejecting meteorites from Mars, the researchers studied their
microscopic make-up with X-ray experiments at Berkeley Lab's Advanced
Light Source (ALS) and at Argonne National Laboratory's Advanced
Photon Source (APS). The X-ray experiments showed that whitlockite
can become dehydrated by such shocks, forming merrillite, a mineral
that is commonly found in Martian meteorites but does not occur
naturally on the Earth. This is important for deducing how much water
could have been on Mars, and whether the water was from Mars itself
rather than comets or meteorites. If even *some* of the merrillite
had been whitlockite before, it changes the water budget of Mars
dramatically. And because whitlockite can be dissolved in water and
contains phosphorus, an essential element for life on Earth -- and
merrillite appears to be common to many Martian meteorites -- the
study could also have implications for the possibility of life on
Mars. The overarching question here is about water on Mars and its
early history on Mars: had there ever been an environment that enabled
a generation of life on Mars? The pressures and temperatures
generated in the shock experiments, while comparable to those of a
meteorite impact, lasted for only about a ten-millionth of a second,
or about one-tenth to one-hundredth as long as an actual meteorite
impact. The fact that experiments showed even partial conversion to
merrillite in lab- created conditions suggested that a longer-duration
impact might have produced 'almost full conversion' to merrillite.

There is also evidence that liquid water flows on Mars today, though
there has not been any scientific proof that life has ever existed on
Mars. In 2013, planetary scientists reported that darkish streaks
that appear on Martian slopes are probably related to periodic flows
of water that result from changing temperatures. They based their
analysis on data from the Mars Reconnaissance Orbiter. And last
November, NASA scientists reported that a large underground body of
water ice in one region of Mars contains the equivalent of all of the
water in Lake Superior, the largest of the Great Lakes in America.
Analyses of surface rocks during Mars rover explorations have also
found evidence of a former abundance of water. The only missing link
now is a proof that merrillite had, in fact, really been Martian
whitlockite before. The team is pursuing another round of studies
using infrared light at the ALS to study actual Martian meteorite
samples, and are also planning X-ray studies of those samples this
year. Many Martian meteorites found on the Earth seem to come from a
period of about 150 to 586 million years ago, and most are probably
from the same region of Mars. These meteorites are probably excavated
from a depth of about a kilometre below the surface by the initial
impact that sent them out into space, so they are not representative
of the more recent 'geology' at the surface of Mars. Most of them are
very similar in composition as well as in the minerals that are
occurring, and have a similar impact age. Mars is likely to have
formed about 4.6 billion years ago, about the same time as
the Earth and the rest of the Solar System. Researchers noted that,
despite detailed studies of Martian meteorites coupled with thermal
imaging of Mars taken from orbiters, and rock samples analyzed by
rovers traversing the planet's surface, the best evidence of Mars'
water history would come actual Martian rocks taken from the planet
and transported back here, intact, for detailed studies.


DAWN IDENTIFES AGE OF CERES' BRIGHTEST AREA
NASA

The bright central area of Ceres' Occator Crater, known as Cerealia
Facula, is approximately 30 million years younger than the crater in
which it lies. Scientists used data from the Dawn spacecraft to
analyze Occator's central dome in detail, concluding that that
intriguing bright feature is only about 4 million years old.
Researchers analyzed data from two instruments on board the spacecraft
-- the framing camera, and the visible and infrared mapping
spectrometer. The new study supports earlier interpretations from the
Dawn team that the reflective material -- the brightest area on Ceres
-- is made of carbonate salts, although it did not confirm a
particular type of carbonate previously identified. The secondary,
smaller bright areas of Occator, called Vinalia Faculae, are comprised
of a mixture of carbonates and dark material. New evidence also
suggests that Occator's bright dome probably rose in a process that
took place over a long period of time, rather than forming in a single
event. The authors of the study believe that the initial trigger was
the impact that dug out the crater itself, causing briny liquid to
rise closer to the surface. Water and dissolved gases, such as carbon
dioxide and methane, came up and created a vent system. The rising
gases could also have forced carbonate-rich materials to ascend toward
the surface. During that period, the bright material would have
erupted through fractures, eventually forming the dome that we see
today.


STAR CLUSTER DISCOVERY UPSETS THEORIES
RAS

The discovery of young stars in old star clusters could send
scientists back to the drawing board for one of the Universe's most
common objects. There is an enormous number of stars in the Universe
and we have been observing and classifying those we can see for more
than a century. Our models of stellar evolution are based on the
assumption that stars within star clusters formed from the same
material at roughly the same time. A star cluster is a group of stars
that share a common origin and are held together by gravity for some
length of time. Because star clusters are assumed to contain stars of
similar age and composition, researchers have used them as 'astronom-
ical laboratories' to understand how mass affects the evolution of
stars. If the assumption turns out to be incorrect, as some findings
suggest, then the important models will need to be revisited and
revised.

The discovery involves a study of star clusters in the Large Magell-
anic Cloud. By cross-matching the locations of several thousand young
stars with the locations of stellar clusters, the researchers found 15
stellar candidates that were much younger than other stars within the
same cluster. The formation of those younger stars might have been
fuelled by gas entering the clusters from interstellar space, but that
possibility was eliminated by observations made by radio telescopes
that showed no correlation between interstellar hydrogen gas and the
locations of the clusters being studied. Scientists believe that the
younger stars have actually been created out of the matter ejected
from older stars as they die, which would mean that we are seeing
multiple generations of stars belonging to the same cluster. The
stars concerned are too faint to see with optical telescopes because
of the dust that surrounds them. They have been observed at infrared
wavelengths by the orbiting space telescopes Spitzer and Herschel.
An envelope of gas and dust surrounds the young stars, but as they
become more massive and that shroud blows away, they will become
visible at optical wavelengths to powerful instruments like the
Hubble Space Telescope. If scientists point Hubble at the clusters
being studied, astronomers should be able to see both young and old
stars and confirm once and for all that star clusters can contain
several generations of stars.


STAR ORBITS BLACK HOLE EVERY 28 MINUTES
Michigan State University

Astronomers have found evidence for a star that orbits a black hole
about twice an hour -- the tightest orbit ever witnessed for a black
hole and a companion star. The discovery team used the Chandra X-ray
Observatory as well as NuSTAR and the Australia Telescope Compact
Array. The close-in stellar binary is located in the globular cluster
47 Tucanae, a dense cluster of stars in our Galaxy about 15,000 light-
years away. While astronomers have observed that binary for many
years, it was not until 2015 that radio observations revealed that the
pair probably contains a black hole pulling material from a white-
dwarf companion, a low-mass star that has exhausted its nuclear fuel.
New Chandra data of the system, which is known as X9, show that it
changes in X-ray brightness in the same manner every 28 minutes, which
is probably the length of time that it takes the companion star to
make one complete orbit around the black hole. Chandra data also show
evidence for large amounts of oxygen in the system -- a characteristic
of white dwarfs. A strong case can, therefore, be made that that the
companion star is a white dwarf, which would then be orbiting the
black hole at only about 2.5 times the separation between the Earth
and the Moon. The white dwarf is so close to the hole that material
is being pulled away from the star and dumped onto a disc of matter
around the black hole before falling in. Although the white dwarf
does not appear to be in immediate danger of falling in or being torn
apart by the black hole, its fate is uncertain.

For a long time astronomers thought that black holes were rare or
absent in globular star clusters. The recent discovery is evidence
that, rather than being one of the worst places to look for black
holes, globular clusters might be one of the best. How did the black
hole get such a close companion? One possibility is that the black
hole smashed into a red-giant star, and then gas from the outer
regions of the star was ejected from the binary. The remaining core
of the red giant would form into a white dwarf, which became a binary
companion to the black hole. The orbit of the binary would then have
shrunk as gravitational waves were emitted, until the black hole
started pulling material from the white dwarf. The gravitational
waves currently being produced by the binary have a frequency that is
too low to be detected with the Laser Interferometer Gravitational-
Wave Observatory, LIGO, that has recently detected gravitational waves
from merging black holes. Sources like X9 could potentially be
detected with future gravitational-wave observatories in space. An
alternative explanation for the observations is that the white dwarf
is partnered by a neutron star, rather than a black hole. In that
scenario, the neutron star spins faster as it pulls material from a
companion star via a disc, a process that can decrease the rotational
period of the neutron star to a few thousandths of a second. A few
such objects, called transitional millisecond pulsars, have been
observed near the end of such a spinning-up phase. The team does not
favour that possibility, as transitional millisecond pulsars have
properties not seen in X9, such as extreme variability at X-ray and
radio wavelengths.


STARDUST SHEDS LIGHT ON FIRST STARS
ESO

A team of astronomers has used the Atacama Large Millimetre/submilli-
metre Array (ALMA) to observe A2744_YD4, the youngest and most remote
galaxy ever seen by ALMA. It was surprised to find that that youthful
galaxy contained an abundance of interstellar dust --- dust formed by
the deaths of an earlier generation of stars. Follow-up observations
using the X-shooter instrument on the Very Large Telescope confirmed
the enormous distance to A2744_YD4. The galaxy appears to us as it
was when the Universe was only 600 million years old, during the
period when the first stars and galaxies were forming. Cosmic dust is
mainly composed of silicon, carbon and aluminium, in grains as small
as a millionth of a centimetre across. The chemical elements in the
grains are forged inside stars and are scattered across the cosmos
when the stars die, most spectacularly in supernova explosions, the
final fate of short-lived, massive stars. Today, such dust is
plentiful and is a key building block in the formation of stars,
planets and complex molecules; but in the early Universe, before the
first generations of stars died out, it was scarce. The observations
of the dusty galaxy A2744_YD4 were made possible because it lies
behind a massive galaxy cluster called Abell 2744. Gravitational
lensing causes the cluster to magnify the more distant A2744_YD4 by
about 1.8 times, allowing the team to peer far back into the early
Universe. The ALMA observations also detected the glowing emission of
ionized oxygen from A2744_YD4. This is the most distant, and hence
earliest, detection of oxygen in the Universe, surpassing another ALMA
result from 2016.

The detection of dust in the early Universe provides new information
on when the first supernovae exploded and hence the time when the
first hot stars bathed the Universe in light. Determining the timing
of that 'cosmic dawn' is one of the 'holy grails' of modern astronomy,
and it can be indirectly probed through the study of early inter-
stellar dust. The team estimates that A2744_YD4 contained an amount
of dust equivalent to 6 million times the mass of the Sun, while the
galaxy's total stellar mass was 2000 million solar masses. The team
also measured the rate of star formation in A2744_YD4 and found that
stars are forming at a rate of 20 solar masses per year, compared to
just one solar mass per year in the Milky Way. That means that
significant star formation began approximately 200 million years
before the epoch at which the galaxy is being observed. That provides
a great opportunity for ALMA to help study the era when the first
stars and galaxies 'switched on' -- the earliest epoch yet probed.


LOST LUNAR SPACECRAFT FOUND
NASA

Finding derelict spacecraft and space debris in orbit round the Earth
is a technological challenge. Detecting such objects in orbit round
the Moon is even more difficult. Optical telescopes are unable to
search for small objects hidden in the bright glare of the Moon.
However, a new technological application of interplanetary radar has
successfully located spacecraft orbiting the Moon -- one active, and
one dormant. The new technique could assist planners of future moon
missions. Scientists have been able to detect NASA's Lunar
Reconnaissance Orbiter [LRO] and the Indian Space Research Organiz-
ation's Chandrayaan-1 spacecraft in lunar orbit with ground-based
radar. Finding LRO was relatively easy, as they were working with the
mission's navigators and had precise orbit data where it was located.
Finding India's Chandrayaan-1 required a bit more detective work
because the last contact with the spacecraft was in 2009 August.
Also, the Chandrayaan-1 spacecraft is very small, a cube about 1.5
metres on a side. Although the interplanetary radar has been used to
observe small asteroids several million miles away, researchers were
not certain that an object of such small size as Chandrayaan-1 as far
away as the Moon could be detected, even with the most powerful
radars. Chandrayaan-1 proved the perfect target for demonstrating the
capability of the technique.

While they all use microwaves, not all radar transmitters are equal.
The average police radar gun has an operational range of about 2 km,
while air-traffic-control radar goes to about 100 km. To find a
spacecraft 380,000 kilometres away, JPL's team used a 70-metre antenna
to send out a powerful beam of microwaves directed toward the Moon.
Then the radar echoes that bounced back from lunar orbit were received
by the 100-metre Green Bank Telescope. The team used data from the
return signal to estimate its velocity and the distance to the target
and its velocity. That information was then used to update the orbital
predictions for Chandrayaan-1. Radar echoes from the spacecraft were
obtained seven more times over three months and are in perfect
agreement with the new orbital predictions.


NASA MISSION NAMED 'EUROPA CLIPPER'
NASA

NASA's upcoming mission to investigate the habitability of Jupiter's
icy moon Europa now has a formal name: Europa Clipper. The moniker
harks back to the clipper ships that sailed across the Earth's oceans
in the 19th century. Clipper ships were streamlined, three-masted
sailing vessels renowned for their grace and swiftness. They rapidly
shuttled tea and other goods back and forth across the Atlantic Ocean
and around the globe. In the grand tradition of those classic ships,
the Europa Clipper spacecraft would sail past Europa at a rapid
cadence, as frequently as every two weeks, providing many opportuni-
ties to investigate the moon up close. The mission plan includes 40
to 45 fly-bys, during which the spacecraft would image the moon's icy
surface at high resolution and investigate its composition and the
structure of its interior and icy shell. Europa has long been a high
priority for exploration because it holds a salty liquid water ocean
beneath its icy crust. The ultimate aim of Europa Clipper is to
determine if Europa is habitable, possessing all three of the
ingredients necessary for life: liquid water, chemical ingredients,
and energy sources sufficient to enable biology. During each orbit,
the spacecraft will spend only a short time within the challenging
radiation environment near Europa. The mission is being planned for
launch in the 2020s, arriving in the Jupiter system after a journey of
several years.

ENB 441

Clive

EVIDENCE FOR ORGANIC MATERIAL ON CERES
NASA

The Dawn mission has found evidence for organic material on Ceres,
a 'dwarf planet' and the largest body in the main asteroid belt
between Mars and Jupiter. Scientists using the spacecraft's 'visible
and infrared mapping spectrometer' (VIR) detected the material in and
around a northern-hemisphere crater called Ernutet. Organic molecules
are interesting to scientists because they are necessary, though not
sufficient, components of life on Earth. The discovery adds to the
growing list of bodies in the Solar System where organics have been
found. Organic compounds have been found in certain meteorites as
well as inferred from telescopic observations of several asteroids.
Ceres shares many commonalities with meteorites rich in water and
organics -- in particular, a meteorite group called carbonaceous
chondrites. This discovery further strengthens the connection between
Ceres, those meteorites and their parent bodies. Data support the
idea that the organic materials are native to Ceres. The carbonates
and clays previously identified on Ceres provide evidence for chemical
activity in the presence of water and heat. That raises the
possibility that the organics were similarly processed in a warm
water-rich environment.

The organics discovery adds to Ceres' attributes associated with
ingredients and conditions for life in the distant past. Previous
studies have found hydrated minerals, carbonates, water ice, and
ammoniated clays that must have been altered by water. Salts and
sodium carbonate, such as those found in the bright areas of Occator
Crater, are also thought to have been carried to the surface by
liquid. The discovery adds to our understanding of the possible
origins of water and organics on Earth. The VIR instrument was able
to detect and map the locations of the material because of its
special signature in near-infrared light. The organic materials on
Ceres are mainly located in an area covering approximately 1,000
square kilometres. The signature of organics is very clear on the
floor of Ernutet Crater, on its southern rim and in an area just
outside the crater to the southwest. Another large area with
well-defined signatures is found across the northwest part of the
crater rim and ejecta. Having completed nearly two years of
observations in orbit at Ceres, Dawn has now made its way to a new
altitude of around 20,000 km, about the height of GPS satellites above
the Earth, and to a different orbital plane. This will put Dawn in a
position to study Ceres in a new geometry. In late spring, Dawn will
view Ceres with the Sun directly behind the spacecraft, such that
Ceres will appear brighter than before, and perhaps reveal more clues
about its nature.


WEB SITE LETS PUBLIC SEARCH FOR NEW WORLDS IN SOLAR SYSTEM
Science Daily

NASA is inviting the public to help search for possible undiscovered
worlds in the outer reaches of our Solar System and in neighbouring
interstellar space. A new web site, called Backyard Worlds: Planet 9,
lets everyone participate in the search by viewing brief movies made
from images captured by NASA's Wide-field Infrared Survey Explorer
(WISE) mission. The movies highlight objects that have gradually
moved across the sky. It is just over four light-years from
Neptune to Proxima Centauri (the nearest star after the Sun), and much
of that vast territory is unexplored. Because there is so little
sunlight, even large objects in that region barely shine in visible
light. But by looking in the infrared, WISE may have imaged objects
we otherwise would have missed. WISE scanned the entire sky between
2010 and 2011, producing the most comprehensive survey at mid-infrared
wavelengths currently available. With the completion of its primary
mission, WISE was shut down in 2011. It was then reactivated in 2013
and given a new mission assisting NASA's efforts to identify
potentially hazardous near-Earth objects (NEOs), which are asteroids
and comets on orbits that bring them into the vicinity of the Earth's
orbit. The mission was re-named the Near-Earth Object Wide-field
Infrared Survey Explorer (NEOWISE). The new web site uses the data to
search for unknown objects in and beyond the Solar System. In 2016,
astronomers at Caltech, in Pasadena, California, showed that several
distant Solar-System objects possessed orbital features indicating
that they were affected by the gravity of an as-yet-undetected planet,
which the researchers nicknamed 'Planet Nine'. If Planet Nine -- also
known as Planet X -- exists and is as bright as some predictions, it
could show up in WISE data. The search also may discover more-distant
objects like brown dwarfs, sometimes called failed stars, in nearby
interstellar space.

Unlike more distant objects, those in or closer to the Solar System
appear to move across the sky at different rates. The best way to
discover them is through a systematic search of moving objects in WISE
images. While parts of this search can be done by computers, machines
are often overwhelmed by image artifacts, especially in crowded parts
of the sky. Those include brightness spikes associated with star
images and blurry blobs caused by light scattered inside WISE's
instruments. Planet 9 relies on human eyes because we easily
recognize the important moving objects while ignoring the artifacts.
It is a 21st-century version of the technique that astronomer Clyde
Tombaugh used to find Pluto in 1930. On the web site, people around
the world can work their way through millions of 'flipbooks', which
are brief animations showing how small patches of the sky changed over
several years. Moving objects flagged by participants will be priori-
tized by the science team for follow-up observations by professional
astronomers. Participants will share credit for their discoveries in
any scientific publications that result from the project. Planet 9 is
potentially a once-in-a-century discovery, and it is exciting to think
that it could be observed first by a citizen scientist.


SPITZER TELESCOPE FINDS SEVEN EARTH-SIZE PLANETS
NASA/Jet Propulsion Laboratory

The Spitzer Space Telescope has revealed the first known system of
seven Earth-size planets around a single star. Three of the planets
are firmly located in the habitable zone, the area around the parent
star where a rocky planet is most likely to have liquid water. The
exo-planet system is 40 light-years away in the constellation of
Aquarius and called TRAPPIST-1, named for The Transiting Planets and
Planetesimals Small Telescope (TRAPPIST) in Chile. In 2016 May,
researchers using TRAPPIST announced that they had discovered three
planets in the system. Assisted by several ground-based telescopes,
including ESO's Very Large Telescope, Spitzer confirmed the existence
of two of the planets and discovered five additional ones, increasing
the number of known planets in the system to seven. Using Spitzer
data, the team precisely measured the sizes of the seven planets and
made initial estimates of the masses of six of them, allowing their
densities to be estimated. On the basis of their densities, all of
the TRAPPIST-1 planets are likely to be rocky. Further observations
will not only help determine whether they are rich in water, but also
possibly reveal whether any could have liquid water on their surfaces.
The mass of the seventh and farthest planet has not yet been estimated
-- scientists believe it could be an icy, 'snowball-like' object --
but further observations are needed.

In contrast to the Sun, the TRAPPIST-1 star -- classified as an
ultra-cool dwarf -- is so cool that liquid water could survive on
planets orbiting very close to it, closer than is possible on planets
in the Solar System. All seven of the TRAPPIST-1 planetary orbits are
closer to their host star than Mercury is to the Sun. The closest one
orbits the star at a distance of only 0.01 AU, and the most distant
one at 0.06 AU. The planets are also very close to one another. If a
person were standing on the surface of one of the planets, he could
gaze up and potentially see the geological features or clouds of
neighbouring ones, which would sometimes appear larger than the Moon
in our sky. The planets are likely to be tidally locked to their
star, which means that the same side of the planet is always facing
the star, therefore each side has either perpetual day or night. That
could mean that they have weather patterns totally unlike those on the
Earth, such as strong winds blowing from the day side to the night
side, and extreme temperature changes.


ASTRONOMERS FIND 100 NEW PLANETS
Carnegie Institution for Science

An international team of astronomers has released the largest-ever
compilation of exo-planet-detecting observations made by the radial-
velocity method. They demonstrated how the observations can be used
to hunt for planets by detecting more than 100 potential exo-planets,
including one orbiting the fourth-closest star to the Solar System,
which is about 8.1 light-years away. The radial-velocity method is
one of the most successful techniques for finding and confirming
planets. It takes advantage of the fact that in addition to a planet
being influenced by the gravity of the star it orbits, the planet's
gravity also affects the star. Astronomers are able to use
sophisticated tools to detect the tiny wobble the planet induces as
its gravity acts on the star. The virtual mountain of data released
to the public in the paper was gathered as part of a 20-year radial-
velocity planet-hunting programme that uses a spectrometer called
HIRES, mounted on the 10-m Keck-I telescope of the Keck Observatory
on Mauna Kea in Hawaii. The compilation includes almost 61,000
individual measurements made of more than 1,600 stars. By making the
data public, the team is offering unprecedented access to one of the
best exo-planet searches in the world. HIRES was not specifically
optimized to do that type of work, but has turned out to be a work-
horse instrument for the field.

Now as the survey moves into its third decade, the team members have
decided on a new stategy. With so many data at hand and a limited
amount of time, they recognized that more exo-planets might be found
if they shared their catalogue with the astronomical community.
But the team is not just giving everyone the keys to its exo-planet
finder; it is also undertaking a sophisticated statistical analysis of
the large data set to try to identify the periodic signals that are
most likely to be planets. Even with the most stringent criteria,
they found over 100 new likely planet candidates. One of them is
around a star called GJ 411, also known as Lalande 21185. It is the
fourth-closest star to the Sun and has only about 40% of the mass
of the Sun. The planet has a very short orbital period of just under
10 days, so it is by no means an Earth twin. However, the inferred
planet, GJ 411 b, continues a trend that has been seen in the overall
population of detected exo-planets: the smallest planets are found
around the smallest stars.


BRIGHTEST AND FARTHEST KNOWN PULSAR
ESA

Astronomers using the XMM-Newton orbiting telescope have found a
pulsar that is a thousand times brighter than was previously thought
possible. The pulsar is also the most distant of its kind ever
detected, with its light travelling 50 million light-years before
being detected by XMM-Newton. Pulsars are spinning, magnetized
neutron stars that sweep regular pulses of radiation across the cosmos
in two symmetrical beams. If suitably aligned with the Earth such
beams are like lighthouse beacons appearing to flash on and off as the
source rotates. Pulsars were once massive stars that exploded as
powerful supernovae at the ends of their natural lives, before
becoming small and extraordinarily dense stellar corpses. The newly
discovered one, an X-ray source, is the most luminous of its type
detected to date: it is 10 times brighter than the previous record-
holder. In one second it emits the same amount of energy as is
released by the Sun in 3.5 years. [A roundabout way of saying that it
is 100 million times brighter. -- ED] XMM-Newton observed the object
several times in the last 13 years; the discovery was a result of a
systematic search for pulsars in the data archive --- its 1.13-second
periodic pulses giving it away.

Previously, it was believed that only black holes at least 10 times
more massive than the Sun feeding off their stellar companions could
achieve such extraordinary luminosities, but the rapid and regular
pulsations of this source are the fingerprints of neutron stars and
clearly distinguish them from black holes. Archival data from NuStar
also revealed that the pulsar's spin rate has changed over time, from
1.43 s per rotation in 2003 to 1.13 s in 2014. The same relative
acceleration in the Earth's rotation would shorten a day by five hours
in the same time span. Only a neutron star is compact enough to keep
itself together while rotating so fast. Although it is not unusual
for the rotation rate of a neutron star to change, the high rate of
change in this case is likely to be linked to the object rapidly
consuming mass from a companion. The scientists think that there must
be a strong, complex magnetic field close to its surface, such that
accretion onto the neutron-star surface is still possible while still
generating the high luminosity.


GIANT RADIO GALAXY DISOVERED
Phys.org

An international team of astronomers reports the discovery of a new
giant radio galaxy (GRG) associated with the galaxy triplet known as
UGC 9555. The newly discovered galaxy turns out to be one of the
largest GRGs so far detected. Located some 820 million light-years
away, UGC 9555 is a part of a larger group of galaxies designated
MSPM 02158. The team has analyzed the data available in the LOFAR
Multifrequency Snapshot Sky Survey (MSSS). The images obtained as a
part of that survey allowed the scientists to distinguish a new giant
radio galaxy. It has not received any official designation yet, but
it has a projected linear size of 8.34 million light-years, making it
one of the largest GRGs known to date.

Currently, with a projected size of approximately 16 million light-
years, an object designated J1420-0545 holds the title of the largest
giant radio galaxy discovered so far. However, the available LOFAR
MSSS of the new GRG and archival radio data are still insufficient to
determine its classification. Radio sources are divided into two
classes: Fanaroff & Riley Class I (FRI) and Class II (FRII). The
researchers concluded that the luminosity suggests that the new object
is a borderline case between FRI and FRII, although the large size and
therefore old age contributes to a decreased luminosity. They hope
that further data gathered from a deep LOFAR observation will clearly
classify the properties of this GRG.


VISIBLE AND DARK MATTER KNOW ABOUT EACH OTHER
Case Western Reserve University

Research by a team of astronomers suggests that the distribution of
normal matter precisely determines gravitational acceleration in all
common types of galaxies. The team has shown that that radial
acceleration relationship exists in nearby high-mass elliptical and
low-mass spheroidal galaxies, adding to last year's discovery of the
relationship in spiral and irregular galaxies. That provides further
support for the idea that the relationship is tantamount to a new
natural law. It may demonstrate that there is a universal law for
galactic systems. That would be analogous to the Kepler law for
planetary systems, which does not care about the specific properties
of the planet: whether the planet is rocky like the Earth or gaseous
like Jupiter, the law applies. The researchers looked at 153 spiral
and irregular galaxies, 25 ellipticals and lenticulars, and 62 dwarf
spheroidals, and found that the observed acceleration tightly
correlates with the gravitational acceleration expected from visible
mass, whatever the type of galaxy. In other words, if astronomers
measure the distribution of normal matter, they know the rotation
curve, and vice versa. But it is still not clear what that
relationship means or what is its fundamental origin. Observed
deviations from the correlation are not related to any specific
galaxy property but completely random and consistent with measurement
errors, .

The tightness of the relationship is difficult to understand in terms
of dark matter as it is currently understood. It also challenges the
current understanding of galaxy formation and evolution, in which many
random processes such as galaxy mergers and interactions, inflows and
outflows of gas, star formation and supernovae, occur at the same
time. To make their discovery, researchers combined different tracers
of the centripetal acceleration found in different types of galaxies,
from which they made one-to-one comparisons. The kinematical tracers
were cold gas in spiral and irregular galaxies, stars or hot gas in
ellipticals and lenticulars, and individual giant stars in dwarf
spheroidals. The investigation included so-called ultra-faint dwarf
spheroidal galaxies, but owing to their faintness --- which makes
them hard to study --- the researchers can not confidently offer a
clear interpretation of the radial acceleration relation in those.
Nevertheless, the growing proof of the relationship, or natural law,
requires new thinking about dark matter and gravity. Within the
standard dark-matter paradigm, the law implies that the visible matter
and the dark matter must be tightly coupled in galaxies at a local
level and independently of global properties: they must 'know about
each other'. Within alternative models like modified gravity, the law
represents a key empirical constraint and may guide theoretical
physicists to build some appropriate mathematical extension of General
Relativity. The team's research so far has focused on galaxies in the
nearby Universe. The team plans to test the relationship in more
distant galaxies, just a few thousand million years after the Big
Bang. It is hoping to learn whether the same relationship holds
throughout the lifetime of the Universe.


NEURAL NETWORKS PROMISE SHARPEST EVER IMAGES
RAS

A telescope is normally limited by the size of the mirror or lens it
uses; its aperture sets a fundamental limit to its performance. Using
'neural nets', a form of artificial intelligence, a group of Swiss
researchers has now found a way to push past that limit, offering
scientists the prospect of the sharpest-ever images in optical
astronomy. A statistical concept known as the Nyquist sampling
theorem describes the resolution limit, and hence how much detail can
be seen. The Swiss authors use the latest in machine-learning
technology to challenge that limit. They teach a neural network, a
computational approach that simulates the neurons in a brain, what
galaxies look like, and then ask it to recover automatically a blurred
image and turn it into a sharp one. Just like a human being, the
neural net needs examples --- in this case a blurred and a sharp image
of the same galaxy --- to learn the technique. The system uses two
neural nets competing with one another, an emerging approach called a
'generative adversarial network', or GAN, popular with the machine-
learning research community. The whole teaching programme took just a
few hours on a high-performance computer.

The trained neural nets were able to recognize and reconstruct
features that the telescope could not resolve -- such as star-forming
regions, bars and dust lanes in galaxies. The scientists checked it
against the original high-resolution image to test its performance,
finding it better able to recover features than anything used to date,
including the 'deconvolution' approach used to improve the images made
in the early years of the Hubble space telescope. Researchers can
start by going back to sky surveys made with telescopes over many
years, see more detail than ever before, and for example learn more
about the structure of galaxies. There is no reason why the technique
cannot then be applied to the deepest images from Hubble, and from the
coming James Webb space telescope, to learn more about the earliest
structures in the Universe. The success of the project points to a
more 'data-driven' future for astrophysics in which information is
learnt automatically from data, instead of manually crafted physics
models.

ENB 440

Clive

HIGHLY ABNORMAL SOLAR ACTIVITY OVER 7,000 YEARS AGO
Nagoya University

An international team of researchers has identified a new type of solar
event and dated it to the year 5480 BC; they did that by measuring
carbon-14 levels in tree rings, which reflect the effects of cosmic
radiation on the atmosphere at the time. They have also proposed causes
of that event. When the activity of the Sun changes, it has direct
effects on the Earth. For example, when the Sun is relatively inactive,
the amount of carbon-14 increases in the Earth's atmosphere. Because
carbon dioxide in the air is absorbed by trees, carbon-14 levels in tree
rings actually reflect solar activity and unusual solar events in the
past. The team took advantage of such a phenomenon by analyzing a
specimen from a bristlecone pine tree, a species that can live for
thousands of years, to look back into the history of the Sun. The team
measured the 14C levels in the pine sample at three different labora-
tories in Japan, the US, and Switzerland, to ensure the reliability of
the results. It found a change in 14C that was more abrupt than any
found previously, except for cosmic-ray events in AD 775 and AD 994, and
the use of annual data rather than data for each decade allowed the team
to pinpoint exactly when the change occurred.

The team attempted to develop an explanation for the anomalous solar-
activity data by comparing the features of the 14C change with those of
other solar events known to have occurred over the last couple of
millennia. Although the newly discovered event was more dramatic than
others found to date, comparisons of the 14C data among them can help us
to work out what happened to the Sun at that time. It is thought that a
change in the magnetic activity of the Sun along with a series of strong
solar bursts, or a very weak Sun, may have caused the unusual tree-ring
data, but the actual mechanism is unknown.


TWO BILLION YEARS OF VOLCANIC ACTIVITY ON MARS
University of Houston

Analysis of a Martian meteorite found in Africa in 2012 has uncovered
evidence of at least 2 billion years of volcanic activity on Mars.
That confirms that Mars may have some of the longest-lived volcanoes
in the Solar System. Shield volcanoes and lava plains form from lava
flowing over long distances, as has happened in the Hawaiian Islands.
The largest Martian volcano, Olympus Mons, is nearly 17 miles high.
That is almost three times the height of the Earth's tallest volcano,
Mauna Kea, at 6.25 miles (the height from the base of its structure,
not from sea level). The findings offer new clues as to how the planet
evolved and insight into the history of volcanic activity on Mars. Much
of what we know about the composition of rocks from volcanoes on Mars
comes from meteorites found on Earth. Analysis of different substances
provides information about the age of the meteorite, its magma source,
length of time in space and how long the meteorite was on the Earth's
surface. Something slammed into the surface of Mars 1 million years
ago, hitting a volcano or lava plain. The impact ejected rocks into
space. Fragments of those rocks crossed the Earth's orbit and fell as
meteorites.

The meteorite known as Northwest Africa 7635 and discovered in 2012 was
found to be a type of volcanic rock called a shergottite. Eleven such
Martian meteorites, with similar chemical composition and ejection time,
have been found, and they came from a similar volcanic source. Given
that they also have the same ejection time, we can conclude that they
came from the same location on Mars. Previously analyzed Martian
meteorites range in age from 327 million to 600 million years old. In
contrast, the 2012 meteorite was formed 2.4 billion years ago and was
ejected from one of the longest-lived volcanic centres in the Solar
System.


PLANETS OF RED DWARFS MAY FACE OXYGEN LOSS
NASA Goddard

The search for life beyond Earth starts in habitable zones, the regions
around stars where conditions could potentially allow liquid water --
which is essential for life as we know it -- to pool on a planet's
surface. New research suggests that some such zones might not actually
be able to support life, owing to frequent stellar eruptions -- which
spew huge amounts of stellar material and radiation out into space --
from young red-dwarf stars. Now scientists want to expand how habitable
zones are defined, taking into account the impact of stellar activity,
which can threaten an exoplanet's atmosphere with oxygen loss. To
determine a star's habitable zone, scientists have previously considered
how much heat and light the star emits. Stars more massive than the Sun
produce more heat and light, so the habitable zone must be farther out.
Smaller, cooler stars have close-in habitable zones. But along with heat
and visible light, stars emit X-ray and ultraviolet radiation, and
produce stellar eruptions such as flares and coronal mass ejections --
collectively called space weather. One possible effect of such radiation
is atmospheric erosion, in which high-energy particles drag atmospheric
molecules, such as hydrogen and oxygen, the ingredients of water, out
into space. The new model for habitable zones now takes that effect into
account.

The search for habitable planets often homes in on red dwarfs, as those
are the coolest, smallest and most numerous stars in the Universe.
On the downside, red dwarfs are also prone to more frequent and powerful
stellar eruptions than the Sun. To assess the habitability of planets
around such stars, we need to understand how those various effects
balance out. Another important habitability factor is a star's age, say
the scientists, on the basis of observations that they have gathered from
the Kepler mission. Every day, young stars produce 'superflares' --
flares and eruptions at least 10 times more powerful than those observed
on the Sun. On their older, matured counterparts resembling our middle-
aged Sun today, such superflares are observed only once every 100 years.
When we look at young red dwarfs in our galaxy, we see they are much
less luminous than the Sun is today. By the classical definition, the
habitable zone around red dwarfs must be 10 to 20 times closer-in than
the Earth is to the Sun. Now we know that red-dwarf stars generate a
lot of X-ray and extreme-ultraviolet emissions that trouble the habitable
zones of exoplanets through frequent flares and stellar storms. Super-
flares cause atmospheric erosion when high-energy X-ray and extreme-
ultraviolet emissions first break molecules into atoms and then ionize
atmospheric gases. During ionization, radiation strikes the atoms and
knocks off electrons. Electrons are much lighter than the newly formed
ions, so they escape gravity's pull far more readily and race out into
space.

Opposites attract, so as more and more negatively-charged electrons are
generated, they create a powerful charge separation that lures positively
charged ions out of the atmosphere in a process called ion escape. The
model estimates the oxygen escape on planets around red dwarfs, assuming
that they do not compensate with volcanic activity or comet bombardment.
Various earlier atmospheric-erosion models indicated that hydrogen is
most vulnerable to ion escape. As the lightest element, it easily
escapes into space, presumably leaving behind an atmosphere rich with
heavier elements such as oxygen and nitrogen. But when the scientists
accounted for superflares, their new model indicated that the violent
storms of young red dwarfs generate enough high-energy radiation to
enable the escape even of oxygen and nitrogen -- building blocks for
life's essential molecules. Considering oxygen escape alone, the model
estimates that a young red dwarf could render a close-in exoplanet
uninhabitable within a few tens to a hundred million years. The loss
of both atmospheric hydrogen and oxygen would reduce and eliminate the
planet's water supply before life would have a chance to develop. The
new habitability model has implications for the recently discovered
planet orbiting the red dwarf Proxima Centauri, our nearest stellar
neighbour. The Earth-sized planet Proxima b orbits Proxima Centauri
20 times closer than Earth is to the Sun. Considering the age of the
host star and how close the planet is to it, the scientists expect that
Proxima b is subjected to torrents of X-ray and extreme-ultraviolet
radiation from superflares occurring roughly every two hours. They
estimate that oxygen would escape from Proxima b's atmosphere in 10
million years. Additionally, intense magnetic activity and stellar wind
-- the continuous flow of charged particles from a star -- exacerbate
already harsh space weather conditions. The scientists concluded that
Proxima b is quite unlikely to be habitable.


WHITE-DWARF PULSAR DISCOVERED
University of Warwick

An exotic binary star system 380 light-years away has been identified
as an elusive white dwarf pulsar -- the first of its kind ever to be
discovered. Astronomers have identified the star AR Scorpii (AR Sco) as
the first white-dwarf version of a pulsar -- objects found in the 1960s
and associated with very different objects called neutron stars. AR Sco
contains a rapidly spinning, burnt-out stellar remnant called a white
dwarf, which lashes its neighbour -- a red dwarf -- with powerful beams
of electrical particles and radiation, causing the entire system to
brighten and fade dramatically twice every two minutes. The latest
research establishes that the lash of energy from AR Sco is a focussed
'beam', emitting concentrated radiation in a single direction -- much
like a particle accelerator -- something which is unique in the known
Universe. AR Sco lies in the constellation Scorpius, 380 light-years
away, quite a close neighbour to us in astronomical terms. The white
dwarf in AR Sco is the size of the Earth but 200,000 times as massive,
and is in a 3.6-hour orbit with a cool star one-third the mass of the
Sun.

With an electromagnetic field 100 million times more powerful than the
Earth's, and spinning in a period just shy of two minutes, AR Sco
produces lighthouse-like beams of radiation and particles, which lash
across the face of the cool star, a red dwarf. As the researchers
previously discovered, that powerful light-house effect accelerates
electrons in the atmosphere of the red dwarf to close to the speed of
light, an effect never observed before in similar types of binary stars.
The distance between the two stars is around 1.4 million kilometres --
three times the distance between the Moon and the Earth. The new data
show that AR Sco's light is highly polarized, showing that the magnetic
field controls the emission of the entire system, just as in neutron-star
pulsars. AR Sco is like a gigantic dynamo: a magnet, the size of the
Earth, with a field that is ~10,000 times stronger than any field that we
can produce in a laboratory, and it is rotating every two minutes. That
generates an enormous electric current in the companion star, which then
produces the variations that we detect in its light.


TAIL OF STRAY BLACK HOLE HIDING IN MILKY WAY
National Astronomical Observatory of Japan

By analyzing the gas motion of an extraordinarily fast-moving cosmic
cloud in a corner of the Milky Way, astronomers found hints of a
wandering black hole hidden in the cloud. That result marks the
beginning of the search for quiet black holes; millions of such objects
are expected to be floating in the Milky Way although only dozens have
been found to date. It is difficult to find black holes, because they
are completely black, though in some cases black holes cause effects
which can be seen. For example, if a black hole has a companion star,
gas streaming into the black hole piles up around it and forms a disc.
The disc heats up through effects of the enormous gravitational pull
of the black hole, and emits intense radiation. But if a black hole is
floating alone in space, no emissions would be observable coming from it.
A research team used the ASTE Telescope in Chile and the 45-m radio
telescope at Nobeyama Radio Observatory to observe molecular clouds
around the supernova remnant W44, located 10,000 light-years away from
us. Their primary goal was to examine how much energy was transferred
from the supernova explosion to the surrounding molecular gas, but they
happened to find signs of a hidden black hole at the edge of W44.

During the survey, the team found a compact molecular cloud with
enigmatic motion. That cloud, named the 'Bullet', has a speed of more
than 100 km/s, which exceeds the speed of sound in interstellar space by
more than two orders of magnitude. In addition, that cloud, with the
size of two light-years, moves backward against the rotation of the Milky
Way Galaxy. To investigate the origin of the Bullet, the team made
intensive observations of the gas cloud. The data indicate that the
Bullet seems to jump out from the edge of the W44 supernova remnant with
immense kinetic energy. Most of the Bullet has an expanding motion with
a speed of 50 km/s, but the tip of the Bullet has a speed of 120 km/s.
Its kinetic energy is a few tens of times larger than that injected by
the W44 supernova. It seems impossible to generate such an energetic
cloud under ordinary environments. The team proposed two scenarios for
the formation of the Bullet. In both cases, a dark and compact gravity
source, possibly a black hole, has an important role. One scenario is
the 'explosion model' in which an expanding gas shell of the supernova
remnant passes by a static black hole. The black hole pulls the gas
very close to it, giving rise to an explosion, which accelerates the gas
toward us after the gas shell has passed the black hole. In that case,
the astronomers estimated that the mass of the black hole to be 3.5 solar
masses or larger. The other scenario is the 'irruption model' in which a
high-speed black hole storms through a dense gas and the gas is dragged
along by the strong gravity of the black hole to form a gas stream. In
that case, researchers estimated that the mass of the black hole would be
36 solar masses or larger. With the present data set, the team can not
distinguish which scenario is more likely. Theoretical studies have
suggested that more than a hundred million black holes should exist in
the Milky Way, although only 60 or so have been identified to date.


BRIDGE OF STARS CONNECTS MAGELLANIC CLOUDS
University of Cambridge

The Magellanic Clouds, the two largest satellite galaxies of the Milky
Way, appear to be connected by a bridge stretching across 43,000 light-
years. For the past 15 years, scientists have been eagerly anticipating
the data from Gaia. The first tranche of information from the satellite
was released three months ago and is freely accessible to everyone. That
data set, of unprecedented quality, is a catalogue of the positions and
brightnesses of a thousand million stars in our Milky Way galaxy and its
environs. The satellite's angular resolution is similar to that of the
Hubble space telescope, but owing to its bigger field of view, it can
cover the entire sky rather than a small portion of it. In fact, Gaia
uses the largest number of pixels of any space-borne instrument to take
digital images of the sky. Better still, the Observatory has not just
one telescope but two, sharing the metre-wide focal plane. Unlike
typical telescopes, Gaia does not just point and stare: it constantly
spins slowly around an axis, sweeping the entire sky in less than a
month, so it not only measures the instantaneous properties of the stars,
but also tracks their changes over time. That provides an opportunity to
find a variety of objects, for example stars that pulsate or explode --
even though that is not what the satellite was primarily designed for.
The Cambridge team concentrated on the area around the Magellanic Clouds
and used the Gaia data to pick out pulsating stars of the type called
RR Lyrae stars, very old and chemically un-evolved. As those stars have
existed since the earliest days of the Clouds' existence, they offer an
insight into the pair's history. Studying the Large and Small Magellanic
Clouds (LMC and SMC respectively) has always been difficult, as they
sprawl out over a large area, but with Gaia's all-sky view, it has become
a much easier task.

Around the Milky Way, the Clouds are the brightest, and largest, examples
of dwarf satellite galaxies. Known to humanity since the dawn of history
(and to Europeans since their first voyages to the Southern Hemisphere),
the Magellanic Clouds have remained an enigma to date. Even though the
Clouds have been a constant fixture of the heavens, astronomers have only
recently been able to study them in any detail. Whether the Clouds fit
the conventional theory of galaxy formation or not depends critically on
their mass and the time of their first approach to the Milky Way. The
researchers at Cambridge's Institute of Astronomy found clues that could
help answer both of those questions. First, the RR Lyrae stars detected
by Gaia were used to trace the extent of the Large Magellanic Cloud. The
LMC was found to possess a fuzzy low-luminosity 'halo' stretching as far
as 20 degrees from its centre. The LMC would only be able to hold on to
the stars at such large distances if it is substantially more massive
than was previously thought, totalling perhaps as much as a tenth of the
mass of the entire Milky Way. An accurate timing of the Clouds' arrival
to the galaxy is impossible without knowledge of their orbits. Unfortun-
ately, the orbits of satellite galaxies are difficult to measure: at
large distances, an object's motion in the sky is so minute that it is
simply unobservable over a human life-span. In the absence of an orbit,
the team found the next-best thing: a stellar stream.

Streams of stars form when a satellite -- a dwarf galaxy or a star
cluster -- starts to feel the tidal force of the body around which it
orbits. The tides stretch the satellite in the direction towards and
away from the host. As a result, on the periphery of the satellite,
two openings form -- small regions where the gravitational pull of the
satellite is balanced by the pull of the host. Satellite stars that
enter those regions find it easy to leave the satellite altogether and
start orbiting the host. Slowly, star after star abandons the satellite,
leaving a luminous trace on the sky, and thus revealing the satellite's
orbit. Stellar streams around the Clouds were predicted but never
observed. Marked by the locations of the Gaia RR Lyrae stars on the sky,
a narrow bridge-like structure connecting the two Clouds could be seen.
It is thought that, at least in part, the 'bridge' is composed of stars
stripped from the Small Cloud by the Large. The rest may actually be
LMC stars pulled from it by the Milky Way.


RECORD-BREAKING BLACK-HOLE ACTIVITY
University of New Hampshire

Astronomers using data from a trio of orbiting X-ray telescopes, NASA's
Chandra X-ray Observatory and Swift satellite as well as ESA's XMM-
Newton, say that a giant black hole ripped apart a nearby star and then
continued to feed off its remains for close to a decade. That black-hole
meal lasted more than 10 times longer than any other previous episode of
a star's death. Dozens of such tidal-disruption events have been
detected since the 1990s, but none that remained bright for nearly as
long as this one. Tidal forces, arising from the intense gravity of the
black hole, can destroy an object -- such as a star -- that wanders too
close. During a TDE, some of the stellar debris is flung outward at high
speeds, while the rest falls toward the black hole. As it travels inward
and is ingested by the black hole, the material heats up to millions of
degrees and generates a distinct X-ray flare. Such multi-wavelength
flares, which can be viewed by the satellites, help to study otherwise
dormant massive back holes. Previous flares were short-lived, typically
becoming very faint in a year, but this super-long X-ray flare has been
persistently bright for close to a decade. The extraordinary long bright
phase of this TDE means that either this was the most massive star ever
to be torn apart during one of these events, or the first where a smaller
star was completely torn apart.

The X-ray source containing the black hole, known by its abbreviated name
of XJ15000154, is located in a small galaxy about 1.8 billion light-
years from the Earth. The X-ray data indicate that radiation from
material surrounding the black hole has consistently surpassed the so-
called Eddington limit, defined by a balance between the outward pressure
of radiation from the hot gas and the inward pull of the gravity of the
black hole. The conclusion that supermassive black holes can grow, from
TDEs and perhaps other means, at rates above those corresponding to the
Eddington limit has important implications. Such rapid growth may help
to explain how supermassive black holes were able to reach masses of about
10 to the 9 solar masses when the Universe was 'only' about one
billion years old. According to modelling by the researchers, the black
hole's feeding supply should be significantly reduced in the next decade
and begin to fade in the next several years.

ENB 439

Clive

METHANE MAY HAVE WARMED MARS
Paulson School of Engineering and Applied Sciences, Harvard

The presence of water on ancient Mars is a paradox. There's plenty of
areographical evidence that rivers periodically flowed across the planet's
surface. Yet in the period of time when those waters are supposed to
have run -- three to four billion years ago -- Mars should have been too
cold to support liquid water. Researchers suggest that early Mars may
have been warmed intermittently by a powerful greenhouse effect. They
found that interactions between methane, carbon dioxide and hydrogen
in the early Martian atmosphere may have created warm periods when the
planet could support liquid water on the surface. Early Mars is
unique in the sense that it is the one planetary environment, other
than the Earth, where we can say with confidence that there were at
least episodic periods when life could have flourished. If we under-
stood how early Mars operated, it could tell us something about the
potential for finding life on other planets outside the Solar System.
Four billion years ago, the Sun was about 30% fainter than it is today
and significantly less solar radiation -- a.k.a. heat -- reached the
Martian surface. The radiation that did reach the planet was trapped
by the atmosphere, resulting in warm, wet periods. For decades,
researchers have struggled to model exactly how the planet was
insulated. The obvious culprit is CO2. Carbon dioxide makes up 95%
of today's Martian atmosphere and is the best-known and most abundant
greenhouse gas on the Earth.

There must have been something else in Mars' atmosphere that
contributed to a greenhouse effect. The atmospheres of rocky planets
lose lighter gases, such as hydrogen, to space over time. (In fact,
the oxidation that gives Mars its distinctive hue is a direct result
of the loss of hydrogen.) The team looked to those long-lost gases --
known as reducing gases -- to provide a possible explanation for Mars'
early climate. In particular, the team looked at methane, which today
is not abundant in the Martian atmosphere. Billions of years ago, however,
areological processes could have been releasing significantly more
methane into the atmosphere. That methane would have been slowly
converted to hydrogen and other gases, in a process similar to that
occurring today on Saturn's moon Titan. To understand how that early
Martian atmosphere may have behaved, the team needed to understand
the fundamental properties of those molecules. In 1977, Carl Sagan first
speculated that hydrogen warming could have been important on early
Mars, but it is only now that scientists have been able to calculate its
greenhouse effect at all accurately. It is also the first time that methane
has been shown to be an effective greenhouse gas on early Mars. This
research shows that the warming effects of both methane and hydrogen
have been underestimated in the past by a significant amount. The
researchers discovered that methane and hydrogen, and their inter-
action with carbon dioxide, were much better at warming early Mars
than had previously been believed. One of the reasons that early Mars
is so fascinating is that life needs complex chemistry to emerge.
Episodes of the emission of reducing gas, followed by planetary
oxidation, could have created favourable conditions for life on Mars.


BOTH PUSH AND PULL DRIVE OUR GALAXY THROUGH SPACE
The Hebrew University of Jerusalem

Although we can't feel it, we are in constant motion: the Earth spins
on its axis at about 1,600 km/h; it orbits around the Sun at about
100,000 km/h; the Sun orbits our Milky Way galaxy at about 850,000
km/h; and the Milky Way galaxy and its companion galaxy Andromeda are
moving with respect to the expanding Universe at roughly 2 million
km/h. But what is propelling the Milky Way's race through space?
Until now, scientists assumed that a dense region of the Universe is
pulling us towards it, in the same way that gravity made Newton's
apple fall to the ground. The initial 'prime suspect' was called the
Great Attractor, a region of half a dozen rich clusters of galaxies
150 million light-years from the Milky Way. Soon after, attention was
drawn to an area of more than two dozen rich clusters, called the
Shapley Concentration, which sits 600 million light-years beyond the
Great Attractor. Now researchers report that our Galaxy is not only
being pulled, but also pushed. In a new study, astronomers describe a
previously unknown, very large, empty region in our extragalactic
neighbourhood. Largely devoid of galaxies, that void exerts what could
be looked upon as a repelling force on our Local Group of galaxies.
By 3-d mapping the flow of galaxies through space, the researchers
found that our Milky Way galaxy is speeding away from a large,
previously unidentified region of low density. Because it repels
rather than attracts, they call this region the Dipole Repeller.
In addition to being pulled towards the known Shapley Concentration,
we are also being pushed away from the newly discovered Dipole
Repeller. Thus it has become apparent that push and pull are of
comparable importance at our location.

The presence of such a low-density region has been suggested
previously, but confirming the absence of galaxies by observation has
proved challenging. But in the new study, researchers tried a
different approach. Using powerful telescopes, among them the Hubble
space telescope, they constructed a 3-dimensional map of the galaxy
flow field. Flows are direct responses to the distribution of matter,
away from regions that are relatively empty and toward regions of mass
concentration; the large-scale structure of the Universe is encoded in
the flow field of galaxies. They studied the peculiar velocities --
those in excess of the Universe's rate of expansion -- of galaxies
around the Milky Way, combining different data sets of peculiar
velocities with a rigorous statistical analysis of their properties.
They thereby inferred the underlying mass distribution that consists
of dark matter and luminous galaxies -- over-dense regions that
attract and under-dense ones whose attraction is less and so seem to
repel. By identifying the Dipole Repeller, the researchers were able
to reconcile both the direction of the Milky Way's motion and its
magnitude. They expect that future ultra-sensitive surveys at optical,
near-infrared and radio wave-lengths will identify the few galaxies
expected to lie in the void, and directly confirm the existence of
that void associated with the Dipole Repeller.


ASTRONOMERS FIND SEVEN DWARF GALAXY GROUPS
National Radio Astronomy Observatory

Dwarf galaxies, nuggets of stars and gas 100 to 1,000 times smaller
than the Milky Way, are thought to be the building blocks of massive
galaxies. Evidence for groups of merging dwarf galaxies, however, has
been lacking until now. Using data from the Sloan Digital Sky Survey
(SDSS) and various optical telescopes, a team of astronomers has
discovered seven distinct groups of dwarf galaxies with just the right
starting conditions to merge eventually and form larger galaxies,
including spiral galaxies like the Milky Way. That discovery offers
compelling evidence that the mature galaxies we see in the Universe
today were formed when smaller galaxies merged many (U.S.)billions of
years ago. Astronomers know that to make a large galaxy, the Universe
has to bring together many smaller galaxies. For the first time, they
have found examples of the first steps in this process -- entire
populations of dwarf galaxies that are all bound together in the same
general neighbourhoods. The team began its search by poring over SDSS
data looking for pairs of interacting dwarf galaxies. It next
examined the images to find specific pairs that appeared to be part of
even larger assemblages of similar galaxies. The researchers then used
the Magellan telescope in Chile, the Apache Point Observatory in New
Mexico, and the Gemini telescope in Hawaii to confirm that the
apparent clusters are not just in the same line of sight but are also
approximately the same distance away, indicating that they are gravi-
tationally bound together. The team hopes that that discovery will
encourage future studies of groups of dwarf galaxies and offer insights
into the formation of galaxies like the Milky Way.


FASTER THAN EXPECTED EXPANSION OF THE UNIVERSE
RAS

By using galaxies as giant gravitational lenses, an international
group of astronomers using the Hubble space telescope has made an
independent measurement of how fast the Universe is expanding. The
newly measured expansion rate for the local Universe is consistent
with earlier findings. Those are, however, in intriguing disagreement
with measurements of the early Universe, that hints at a fundamental
problem at the very heart of our understanding of the cosmos. The
Hubble constant -- the rate at which the Universe is expanding -- is
one of the fundamental quantities describing our Universe. A group of
astronomers from the H0LiCOW collaboration used the Hubble telescope
and other telescopes, in space and on the ground, to observe five
galaxies in order to arrive at an independent measurement of the
Hubble constant. The new measurement is completely independent of,
but in excellent agreement with, other measurements of the Hubble
constant in the local Universe that used Cepheid variable stars and
supernovae as points of reference. However, the value obtained by the
team, as well as the values from Cepheids and supernovae, differ from
the measurement made by the Planck satellite. But there is an
important distinction -- Planck measured the Hubble constant for the
early Universe by observing the cosmic microwave background. While
the value for the Hubble constant determined by Planck fits with our
current understanding of the cosmos, the values obtained by the
various groups of astronomers for the local Universe disagree with
the accepted theoretical model of the Universe. The expansion rate
of the Universe is now starting to be measured in different ways with
such high precision that actual discrepancies may possibly point
towards new physics beyond our current knowledge of the Universe.

The targets of the study were massive galaxies positioned between the
Earth and very distant quasars. The light from the more distant
quasars is bent around the huge masses of the galaxies as a result of
strong gravitational lensing. That creates multiple images of the
background quasar, some of them smeared into extended arcs. Because
galaxies do not create perfectly spherical distortions in the fabric
of space and the lensing galaxies and quasars are not perfectly
aligned, the light that forms the different images of the background
quasar follows paths which have slightly different lengths. Since
the brightness of quasars changes over time, astronomers can see the
different images flicker at different times; the delays between them
depend on the lengths of the paths that the light has taken. The
delays are directly related to the value of the Hubble constant.
That method is the simplest and most direct way to measure the Hubble
constant, as it uses only geometry and General Relativity, no other
assumptions. Use of the accurate measurements of the time delays
between the multiple images, as well as computer models, has allowed
the team to determine the Hubble constant to a rather high precision,
3.8%. The Hubble constant is crucial for modern astronomy as it can
help to confirm or refute whether our picture of the Universe --
composed of dark energy, dark matter and normal matter -- is actually
correct, or if we are missing something fundamental.

NEW TEST FOR LIFE ON OTHER PLANETS
NASA

A simple chemical method could greatly enhance how scientists search
for signs of life on other planets. The test uses a liquid-based
technique known as capillary electrophoresis to separate a mixture of
organic molecules into its components. It was designed specifically
to look for amino acids, the structural building blocks of all life on
Earth. The method is 10,000 times more sensitive than current methods
employed by spacecraft like the Mars Curiosity rover, according to a
new study carried out by researchers from the JPL in Pasadena. One of
the key advantages of the new way of using capillary electrophoresis
is that the process is relatively simple and easy to automate for the
liquid samples expected on ocean-world missions: it involves combining
a liquid sample with a liquid reagent, followed by chemical analysis
under conditions determined by the team. By shining a laser across
the mixture -- a process known as laser-induced fluorescence detection
-- specific molecules can be observed moving at different speeds.
They get separated on the basis of how quickly they respond to
electric fields. While capillary electrophoresis has been known since
the early 1980s, this is the first time that it has been tailored
specifically to detect extra-terrestrial life on an ocean world.
The method improves on previous attempts by increasing the number of
amino acids that can be detected in a single run. Additionally, it
allows scientists to detect the amino acids at very low concentra-
tions, even in very salty samples, with a very simple 'mix and analyze'
process.

The researchers used the technique to analyze amino acids present in
the salt-rich waters of Mono Lake in California. The lake's excep-
tionally high alkaline content makes it a challenging habitat for
life, and an excellent stand-in for salty waters believed to be on
Mars, or the ocean worlds of Saturn's moon Enceladus and Jupiter's
moon Europa. The researchers were able simultaneously to analyze 17
different amino acids, which they are calling 'the Signature 17
standard'. Those amino acids were chosen for study because they are
the ones most commonly found on the Earth or elsewhere. Using that
method, it is possible to distinguish between amino acids that come
from non-living sources like meteorites and those that come from
living organisms. The key to detecting amino acids related to life is
an aspect known as chirality. Chiral molecules such as amino acids
come in two forms that are mirror images of one another. Although
amino acids from non-living sources contain approximately equal
amounts of the 'left'- and 'right'-handed forms, amino acids from
living organisms on Earth are almost exclusively the 'left-handed'
form. It is expected that amino-acid life elsewhere would also need
to 'choose' one of the two forms in order to create the structures of
life. For that reason, chirality of amino acids is considered one of
the most powerful signatures of life. One of NASA's highest-level
objectives is the search for life in the Universe. Our best chance of
finding life on worlds physically accessible by spacecraft may lie in
the use of powerful liquid-based analyses like the one tried on Mono
Lake.


NEW PLANET IMAGER DELIVERS FIRST SCIENCE
NASA

A new device on the Keck Telescope in Hawaii has delivered its first
images, showing a ring of planet-forming dust around a star, and
separately, a brown dwarf (a cool, star-like body), lying near its
companion star. The device, called a vortex coronagraph, was recently
installed inside NIRC2 (Near Infrared Camera 2), the workhorse
infrared imaging camera at Keck. It can image planetary systems and
brown dwarfs closer to their host stars than any other instrument in
the world. The vortex study has obtained the first direct image of
the brown dwarf called HIP 79124 B. That brown dwarf is located 23
astronomical units from a star in a nearby star-forming region called
Scorpio-Centaurus. The ability to image objects that are very close
to stars also allows astronomers to search for planets around more
distant stars, where the planets and stars would appear closer
together. Being able to survey distant stars for planets is important
for catching planets still forming. The second vortex study presents
an image of the innermost of three rings of dusty, planet-forming
material around a young star called HD 141569 A. The results, when
combined with infrared data from the Spitzer, WISE, and Herschel
missions, reveal that the star's planet-forming material is made up of
pebble-size grains of olivine, one of the most abundant silicates in
the Earth's mantle. The data also show that the temperature of the
innermost ring imaged by the vortex is about 100 degrees K, slightly
less cold than our asteroid belt.

ENB 438

Clive

NEW THEORY ON MOON FORMATION
American Technion Society

The Moon, and the question of how it was formed, has long been a
source of fascination and wonder. Now, a team of Israeli researchers
suggests that the Moon we see now is not the Earth's first moon, but
rather the last in a series of moons that orbited the Earth in the
past. The new proposal runs counter to the commonly held 'giant
impact' paradigm that the Moon is a single object that was formed
following a single great collision between a small Mars-like planet
and the ancient Earth. The new model is consistent with science's
current understanding of the formation of the Earth. In its last
stages of growth, the Earth experienced many giant impacts with other
bodies. Each of those impacts contributed more material to the
proto-Earth, until it reached its current size. The new theory
suggests that the Earth had many previous moons, and a previously
formed moon could therefore already exist when another moon-forming
giant impact occurred. The tidal forces from the Earth could cause
moons to migrate slowly outwards (the current Moon is slowly doing
that, at a rate of about 1 cm a year). A pre-existing moon would
slowly move out by the time another moon forms. However, their mutual
gravitational attraction would eventually cause the moons to affect
one another and change their orbits. That model suggests that the
ancient Earth once hosted a series of moons, each one formed from a
different collision with the proto-Earth. It is likely that such
moonlets were later ejected, or collided with the Earth or with one
another to form bigger moons.


VLT TO SEARCH FOR PLANETS IN ALPHA CENTAURI SYSTEM
ESO

ESO has signed an agreement with 'Breakthrough Initiatives' to adapt
the Very Large Telescope instrumentation in Chile to conduct a search
for planets in the 'nearby' star system Alpha Centauri. Such planets
could be the targets for an eventual launch of miniature space probes
by the 'Breakthrough Starshot' initiative. The discovery in 2016 of a
planet, Proxima b, around Proxima Centauri, faintest of the three
stars of the Alpha Centauri system, adds further impetus to the
search. Knowing where the nearest exo-planets are is of paramount
interest for 'Breakthrough Starshot', a research and engineering
programme launched in 2016 April, which aims to demonstrate proof of
concept for ultra-fast light-driven 'nanocraft', laying the
foundation for the first launch to Alpha Centauri within a generation.
Detecting a habitable planet is an enormous challenge, owing to the
brightness of the planetary system's host star, which tends to
overwhelm the relatively dim planets. One way to make that easier is
to observe in the mid-infrared wavelength range, where the thermal
glow from an orbiting planet greatly reduces the brightness gap
between it and its host star. But even in the mid-infrared, the star
remains millions of times brighter than the planets to be detected,
which calls for a dedicated technique to reduce the blinding stellar
light.

The existing mid-infrared instrument VISIR on the VLT would provide
such performance if it were enhanced to improve the image quality by
adaptive optics, and adapted to employ coronagraphy to reduce the
stellar light and thereby reveal the possible signals of potential
terrestrial planets. 'Breakthrough Initiatives' will pay for a large
fraction of the necessary technology and development costs for such an
experiment, and ESO will provide the required observing capabilities
and time. Detecting and studying potentially habitable planets
orbiting other stars will be among the main scientific goals of the
upcoming European Extremely Large Telescope (E-ELT). Although the
larger size of the E-ELT will be essential to obtaining an image of
a planet at greater distances in the Milky Way, the light-collecting
power of the VLT is just sufficient to image a planet around the
nearest star, Alpha Centauri.


ORBIT OF PROXIMA CENTAURI DETERMINED
ESO

Interest in our neighbouring Alpha Centauri star system has been
particularly high since the recent discovery of an Earth-mass planet,
known as Proxima b, orbiting the system's third star -- the closest
star to the Sun -- Proxima Centauri. While the system's larger
stellar pair, Alpha Centauri A and B, appears to have a proper motion
on the sky that is very similar to that of the smaller, fainter
Proxima Centauri, it has not been possible to demonstrate that the
three stars do actually form a single, gravitationally bound, triple
system. Now astronomers have concluded that the three stars do
indeed form a bound system. In the century since Proxima was
discovered, its faintness has made it extremely difficult to measure
its radial velocity reliably. But now ESO's planet-hunting HARPS
instrument has provided an extremely precise measurement of Proxima's
radial velocity, and even greater accuracy has been achieved by
accounting for other subtle effects. As a result, the astronomers
have been able to deduce very similar values for the radial velocities
of the Alpha Centauri pair and Proxima Centauri, lending credence to
the idea that they form a bound system. Taking account of the new
measurements, calculations of the orbits of the three stars indicate
that the relative velocity between Proxima Centauri and the Alpha
Centauri pair is well below the threshold above which the three stars
would not be bound together by gravity.

That result has significant implications for our understanding of the
Alpha Centauri system and the formation of planets there. It strongly
suggests that Proxima Centauri and the Alpha Centauri pair are the
same age (about 6,000 million years), and that in turn provides a good
estimate of the age of the orbiting planet, Proxima b. The astronomers
speculate that the planet may have formed around Proxima Centauri on
a more extended orbit and then been brought to its current position,
very close to its parent star, as a result of a close passage of
Proxima to its cousins in the Alpha Centauri pair. Alternatively, the
planet may have formed around the Alpha Centauri pair, and was later
captured by the gravity of Proxima. If one of those hypotheses is
correct, it is possible that the planet was once an icy world that
underwent a meltdown and now may have liquid water on its surface.


TWO MISSIONS TO DETECT EARLY SOLAR SYSTEM
Science Daily

NASA has selected two missions that have the potential to open new
windows on one of the earliest eras in the history of the Solar System
-- a time less than 10 million years after the birth of the Sun. The
missions, known as Lucy and Psyche, were chosen from five finalists
and will proceed to mission formulation, with the goal of launches
in 2021 and 2023, respectively. Lucy will visit the environment of
Jupiter's Trojan asteroids, while Psyche will study a unique metallic
asteroid that has not been visited before.

Lucy is scheduled to be launched in 2021 October. It is intended to
arrive at its first destination, a main-belt asteroid, in 2025. From
2027 to 2033, Lucy will explore six Trojan asteroids. Those asteroids
are trapped by Jupiter's gravity in two swarms that share the planet's
orbit, one leading and one trailing Jupiter by 60 degrees in its
12-year circuit round the Sun. The Trojans are thought to be relics
of a much earlier era in the history of the Solar System, and may have
been formed far beyond Jupiter's current orbit.

The Psyche mission will explore one of the most intriguing objects in
the main asteroid belt -- the big metal asteroid 16 Psyche, about
three times further away from the Sun than the Earth is. It is about
210 kilometres in diameter and, unlike most other asteroids, that are
rocky or icy bodies, is thought to be composed mostly of metallic iron
and nickel, like the Earth's core. Scientists wonder whether Psyche
could be the exposed core of an early planet that could have been as
large as Mars, but which lost its rocky outer layers owing to a number
of violent collisions millions of years ago. The mission will help
scientists to understand how planets and other bodies separated into
their layers -- including cores, mantles and crusts -- early in their
histories. Psyche is intended to be launched in 2023 October,
arriving at the asteroid in 2030, following an Earth-gravity-assist
manoeuvre in 2024 and a Mars-flyby in 2025.


STAR PREDICTED TO EXPLODE IN 2022
Earth and Sky

Astronomers have made an unprecedented prediction of a star explosion
due in the year 2022 or thereabouts; they say that it will be visible
from the Earth, even to those without telescopes. The star system is
an eclipsing binary known as KIC 9832227. New evidence suggests that
the two very close stars are getting closer and soon will merge
explosively. The prediction, originally made in 2015, is that the two
stars in the KIC 9832227 system will get closer and closer and finally
merge and explode in 2022, give or take a year. When that happens,
the star will increase its brightness ten thousandfold, temporarily
becoming a bright star. The star will be visible in the constellation
Cygnus, adding a star as bright as 2nd magnitude to the familiar
pattern.

The team's exploration of the KIC 9832227 system began in 2013 when
it looked at how the colour of the star correlated with brightness and
determined that it was definitely a binary. In fact, it was actually
a contact binary, in which the two stars share a common atmosphere,
like two peanuts sharing a single shell. A precise orbital period
(just under 11 hours) was determined from Kepler satellite data, and
astronomers were surprised that the period was slightly shorter than
that shown by earlier data. That result brought to mind work published
by astronomer Romuald Tylenda, who had studied the observational
archives to see how another star (V1309 Scorpii) had behaved before
it exploded unexpectedly in 2008 and produced a red nova (a type of
stellar explosion only recently recognized as distinct from other
types). The pre-explosion record showed a contact binary with an
orbital period decreasing at an accelerating rate. That pattern of
orbital change was a 'Rosetta stone' for interpreting the new data.
In the past two years, the team has been performing observational
tests, which ruled out other explanations and strengthened the belief
that KIC 9832227 will soon explode. The team believes that the
merging-star hypothesis should be taken seriously, and astronomers
should be using the next few years to study the system intensely, so
that if it does blow up we will know what led to that explosion.
To that end, the team will be observing KIC 9832227 in the next year
over the full range of wavelengths, using the Very Large Array, the
Infrared Telescope Facility, and the XMM-Newton spacecraft, to study
the star's radio, infrared and X-ray emission, respectively. The
orbital timing can be checked by amateur astronomers. They can
measure the brightness variations of this 12th-magnitude star as it
eclipses, and see for themselves if it is continuing on the schedule
that is predicted or not.


MISSING LINK NEUTRON STAR
NASA

Astronomers have found that a misfit 'skeleton' of a star may link two
different kinds of stellar remains. The object, called PSR J1119-6127,
has been caught behaving like two distinct objects -- a radio pulsar
and a magnetar -- and could be important to understanding their
evolution. A radio pulsar is type of a neutron star -- the extremely
dense remnant of an exploded star -- that emits radio waves in
predictable pulses owing to its fast rotation. Magnetars, by contrast,
have violent, high-energy outbursts of X-ray and gamma-ray light, and
their magnetic fields are the strongest known in the Universe. Since
the 1970s, scientists have treated pulsars and magnetars as two
distinct populations of objects, but in the last decade evidence has
emerged that they could be stages in the evolution of a single object.
The new study, combined with other observations of the object,
suggests that J1119 could be in a never-before-seen transition state
between radio pulsar and magnetar. When the object was discovered in
2000, it appeared to be a radio pulsar. It was mostly quiet and
predictable until last July, when the Fermi and Swift space
observatories observed two X-ray bursts and 10 additional bursts of
light at lower energies coming from the object. When the outbursts
happened, astronomers used the Deep Space Network 70-m radio telescope
in Canberra -- the largest dish in the southern hemisphere -- to see
what was going on. It is believed that the X-ray bursts happened
because the object's enormous magnetic field became twisted as the
object was spinning. The stress of a twisting magnetic field is so
great that it causes the outer crust of the neutron star to break --
analogous to tectonic plates on the Earth causing earthquakes. That
causes an abrupt change in rotation, which has been measured by
NuSTAR.

Neutron stars are so dense that one teaspoonful has the mass of a
mountain. The star's crust, roughly 1 kilometre thick, with higher
pressure and density at greater depths, is a neutron-rich lattice.
This particular neutron star is thought to have one of the strongest
magnetic fields among the population of known pulsars: a few times 10
to the 12 times stronger than the magnetic field of the Sun. Two
weeks after the X-ray outburst, astronomers tracked the object's
emissions at radio frequencies. The radio emissions had sharp
increases and decreases in intensity, allowing scientists to quantify
how the emission evolved. Researchers used an instrument, which they
informally call a 'pulsar machine', that was recently installed at the
same DSN dish in Australia. Within 10 days, something completely
changed in the pulsar. It started behaving like a normal radio pulsar
again. The question remains: which came first, the pulsar or the
magnetar? Some scientists argue that objects like J1119 begin as
magnetars and gradually stop outbursting X-rays and gamma rays over
time. But others propose the opposite theory: that the radio pulsar
comes first and, over time, its magnetic field emerges from the
supernova's rubble, and then the magnetar-like outbursts begin. To
help solve the problem, astronomers want to find more 'missing link'
objects like J1119. That particular object was probably formed by
a supernova 1,600 years ago. Monitoring similar objects may shed
light on whether the phenomenon is specific to J1119, or whether such
behaviour is common in that class of objects.


HUBBLE PROVIDES ROAD MAP FOR VOYAGERS' GALACTIC TREK
Space Telescope Science Institute (STScI)

The two Voyager spacecraft are hurtling through unexplored territory
on their trip beyond the Solar System. Along the way, they are
measuring the interstellar medium. The Hubble telescope is providing
the road map, by measuring the material along the probes' future
trajectories as they move through space. Even after the Voyagers run
out of electrical power and are unable to send back new data, which
may happen in about a decade, astronomers can use Hubble observations
to characterize their environment. A preliminary analysis of the
Hubble observations reveals a rich, complex interstellar ecology,
containing multiple clouds of hydrogen laced with other elements.
Hubble data, combined with the Voyagers, have also provided new
insights into how the Sun travels through interstellar space. The
Voyagers are sampling tiny regions as they travel through space at
roughly 38,000 miles per hour. But we have no idea if these small
areas are typical or rare. NASA launched the twin Voyager 1 and 2
spacecraft in 1977. Both explored the outer planets Jupiter and
Saturn, and Voyager 2 went on to visit Uranus and Neptune.

The pioneering Voyager spacecraft are currently exploring the
outermost edge of the Sun's domain. Voyager 1 is now in interstellar
space, the region between the stars that is filled with gas, dust, and
material recycled from dying stars. Voyager 1 is 13,000 million miles
from the Earth. In about 40,000 years (long after it ceases to be
operational, of course), it will pass within 1.6 light-years of the
star Gliese 445, in the constellation Camelopardus. Its twin, Voyager
2, is 10,500 million miles away, and will pass 1.7 light-years from
the star Ross 248 in about 40,000 years. For the next 10 years, the
Voyagers will be making measurements of interstellar material,
magnetic fields, and cosmic rays along their trajectories. Hubble
complements the Voyagers' observations by looking at two sight-lines
along each spacecraft's path to map interstellar structure along their
routes. Each sight-line stretches several light-years to nearby
stars. Sampling the light from those stars, Hubble's 'Imaging
Spectrograph' measured how interstellar material absorbed some of the
starlight, leaving telltale spectral fingerprints. Hubble found that
Voyager 2 will move out of the interstellar cloud that surrounds the
Solar System in a couple of thousand years.


FARTHEST STARS IN MILKY WAY
Harvard-Smithsonian Center for Astrophysics

The 11 farthest known stars in our galaxy are located about 300,000
light-years away, well outside the Milky Way's spiral disc. New
research by Harvard astronomers shows that half of those stars might
have come from another galaxy, the Sagittarius dwarf. Moreover, they
are members of a long stream of stars extending for a million light-
years across space -- 10 times the diameter of our Galaxy. The
Sagittarius dwarf is one of dozens of mini-galaxies that surround the
Milky Way. Over the age of the Universe it has made several loops
around our Galaxy. On each passage, the Milky Way has raised
gravitational tides on the smaller galaxy, pulling it apart.
Researchers used computer models to simulate the movements of the
Sagittarius dwarf over the past 8 billion years. They varied the
initial velocity and angle of approach to the Milky Way to determine
what best matched current observations. At the beginning of the
simulation, the Sagittarius dwarf had a mass of about 10 to the 10
times the mass of our Sun, or about one per cent of the Milky Way's
mass. The calculations showed that, over time, the dwarf galaxy lost
about a third of its stars and a full nine-tenths of its dark matter.
That resulted in three distinct streams of stars that reach as far as
a million light-years from the Milky Way's centre. They stretch all
the way out to the edge of the Milky Way halo and display one of the
largest structures observable on the sky. Moreover, five of the 11
most distant stars in our Galaxy have positions and velocities that
match what would be expected of stars stripped from the Sagittarius
dwarf. The other six do not appear to be from Sagittarius, but might
have been removed from a different dwarf galaxy. Mapping projects
like the Sloan Digital Sky Survey have charted one of the three
streams predicted by the simulations, but not to the full extent that
the models suggest. Future instruments like the Large Synoptic Survey
Telescope, which will detect much fainter stars across the sky, may be
able to identify the other streams.


PHOTONS STRUGGLE TO ESCAPE DISTANT GALAXIES
RAS

Astronomers have discovered giant haloes around early Milky-Way-type
galaxies, made of photons that have struggled to escape them. In
order to understand how our own Milky Way galaxy formed and evolved,
astronomers rely on observing distant galaxies. With the most distant
galaxies, only one spectral feature typically stands out, the Lyman-
alpha line associated with hydrogen gas. Newly born stars in very
distant galaxies are hot enough to ionize hydrogen in surrounding
clouds of gas, which then shine brightly in Lyman-alpha light, in
theory the strongest such feature observable in a distant galaxy. Yet
in practice, Lyman-alpha photons struggle to escape galaxies, as gas
and dust block and deviate their travel paths, making it a complex
process to understand. Using the Isaac Newton telescope on La Palma,
astronomers developed a unique experiment to study almost 1000 distant
galaxies. They surveyed the sky with the Wide-Field Camera and
custom-made filters, in order to measure where the Lyman-alpha is
produced, how much of it there is, and where it comes out of galaxies.

The results show that only 1-2% of those photons escape from the
centres of galaxies like the Milky Way. Even if we account for all the
photons at a large distance from the centre, fewer than 10% escape.
Galaxies forming stars in the distant Universe seem to be surrounded
by an impressively large, faint halo of Lyman-alpha photons that had
to travel for hundreds of thousands of light-years in an almost
endless series of absorption and re-emission events, until they were
finally free. Scientists now need to understand exactly how and why
that happens. When the James Webb space telescope begins operation in
2018, astronomers expect to be able to look even further back in time,
opening up a new window on the first galaxies and stars. Studying how
the escape fraction evolves over time can tell us about the kind of
stars producing the Lyman-alpha photons, and the properties of inter-
stellar and intergalactic gas.

ENB 437

Clive

DETECTION OF BORON ON MARS
Los Alamos National Laboratory

Data from NASA's Curiosity rover reveal that boron has been identified
for the first time on the surface of Mars, indicating that groundwater
offering the potential for long-term habitability existed on Mars in
the distant past. If the boron that was found in calcium-sulphate
mineral veins on Mars is analogous to what we see on Earth, it would
indicate that the groundwater of ancient Mars that formed the veins
would have been at 0 to 60 degrees Celsius and neutral-to-alkaline pH.
The temperature, pH, and dissolved mineral content of the groundwater
could make it habitable. The boron was identified by the rover's
laser-shooting 'Chemistry and Camera' ('Chem Cam') instrument. Boron
is associated on Earth with arid sites where much water has evaporated
away. However, the environmental implications of the boron found by
Curiosity are still open to debate. Scientists are considering at
least two possibilities for the source of the boron that ground water
left in the veins. It could be that the drying out of part of Gale
lake resulted in a boron-containing deposit in an overlying layer, not
yet reached by Curiosity. Some of the material from that layer could
later have been carried by groundwater down into fractures in the
rocks. Or perhaps changes in the chemistry of clay-bearing deposits
and groundwater affected how boron was picked up and dropped off
within the local sediments.

The discovery of boron is only one of several recent findings related
to the composition of Martian rocks. Curiosity is climbing a layered
Martian mountain and finding rock-composition evidence of how ancient
lakes and wet underground environments changed, thousands of millions
of years ago, in ways that affected their favourability for microbial
life. As the rover has progressed uphill, compositions trend toward
more clay and more boron. Those and other variations can tell us
about conditions under which sediments were initially deposited and
about how later groundwater moving through the accumulated layers
altered and transported ingredients. Groundwater and chemicals
dissolved in it that appeared later on Mars left their effects most
clearly in mineral veins that filled cracks in older layered rock.
But they also affected the composition of the rock matrix surrounding
the veins, and the fluid was in turn affected by the rock. Whether
life has ever existed on Mars is still unknown. No compelling
evidence for it has been found. When Curiosity landed in Mars' Gale
Crater in 2012 the mission's main goal was to determine whether the
area ever offered an environment favourable for microbes. Four recent
drilling sites, from 'Oudam' this past June to 'Sebina' in October,
are spaced about 25 metres apart in elevation. Their uphill pattern
allows the scientific team to sample progressively younger layers that
reveal Mount Sharp's ancient environmental history. Variations in
those minerals and elements indicate a dynamic system. They interact
with groundwater as well as surface water. The water influences the
chemistry of the clays, but the composition of the water also changes.
We are seeing chemical complexity indicating a long, interactive
history with the water. The more complicated the chemistry is, the
better it is for habitability. The boron and clay underline the
mobility of elements and electrons, and that is good for life.


WHERE IS THE ICE ON CERES?
NASA

At first glance, Ceres, the largest body in the main asteroid belt,
does not look icy. Images from the Dawn spacecraft have revealed a
dark, heavily cratered world whose brightest area is made of highly
reflective salts -- not ice. But newly published studies from Dawn
scientists show two distinct lines of evidence for ice at or near the
surface. Those studies support the idea that ice separated from rock
early in Ceres' history, forming an ice-rich crustal layer, and that
ice has remained near the surface over the history of the Solar
System. Water ice on other planetary bodies is important because it
is an essential ingredient for life as we know it. By finding bodies
that were water-rich in the distant past, we may discover clues as to
where life may have existed in the early Solar System. Ceres'
uppermost surface is rich in hydrogen, with higher concentrations at
mid-to-high latitudes -- consistent with broad expanses of water ice.
On Ceres, ice is not just localized to a few craters. It is every-
where, and nearer to the surface at higher latitudes. Researchers
used the GRaND instrument to determine the concentrations of hydrogen,
iron and potassium in the uppermost metre of Ceres. GRaND measures
the number and energy of gamma rays and neutrons emanating from Ceres.
Neutrons are produced as Galactic cosmic rays interact with Ceres'
surface. Some neutrons get absorbed into the surface, while others
escape. Since hydrogen slows down neutrons, it is associated with
fewer neutrons escaping. On Ceres, hydrogen is likely to be in the
form of frozen water.

Researchers found that, rather than a solid ice layer, there is likely
to be a porous mixture of rocky materials in which ice fills the pores.
The GRaND data show that the mixture is about 10% ice by weight. That
result confirms predictions made nearly 30 years ago that ice can
survive for thousands of millions of years just beneath the surface of
Ceres. The evidence strengthens the case for the presence of near-
surface ice on other main-belt asteroids. Ceres' brightest area, in
the northern-hemisphere crater Occator, does not shine because of ice,
but rather because of highly reflective salts. Occator's central
bright region, which includes a dome with fractures, has recently been
named Cerealia Facula. The crater's cluster of less-reflective spots
to the east of the centre is called Vinalia Faculae.

Dawn began its 'extended mission' phase last July, and is currently in
an elliptical orbit more than 7,200 km from Ceres. During the primary
mission, Dawn orbited and accomplished all of its original objectives
at Ceres and at the proto-planet Vesta, which the spacecraft visited
from 2011 July to 2012 September.


MOST OUTER PLANETS HAVE NEPTUNE MASS
NASA/Goddard Space Flight Center

A new statistical study of planets found by a technique called
gravitational microlensing suggests that Neptune-mass worlds are
likely to be the most common type of planet to form in the icy outer
realms of planetary systems. The study provides the first indication
of the types of planets waiting to be found far from their host stars,
where scientists suspect planets form most efficiently. Gravitational
microlensing occurs through the light-bending effects, predicted by
Einstein's general theory of relativity, of massive objects. It occurs
when a foreground star, the lens, randomly aligns with a distant
background star, the source, as seen fromthe Earth. As the lensing
star drifts along in its orbit around the galaxy, the alignment shifts
over days to weeks, changing the apparent brightness of the source.
The precise pattern of the changes offers clues about the nature of
the lensing star, including any planets it may host. More than 50
exoplanets have been discovered through microlensing, compared to
thousands detected by other techniques, such as detecting the motion
or dimming of a host star caused by the presence of planets. Because
the necessary alignments between stars are rare and occur randomly,
astronomers must monitor millions of stars for the tell-tale bright-
ness changes that signal a microlensing event. However, microlensing
holds great potential. It can detect planets hundreds of times more
distant than most other methods, allowing astronomers to investigate a
broad swath of our Milky Way galaxy. The technique can locate exo-
planets of smaller masses and at greater distances from their host
stars, and it is sensitive enough to find planets floating through
the Galaxy on their own, not bound to stars.

The Kepler and K2 missions have been extraordinarily successful in
finding planets that dim their host stars, with more than 2,500
confirmed discoveries to date. That technique is sensitive to
close-in planets but not to distant ones. Microlensing surveys are
complementary, best probing the outer parts of planetary systems with
less sensitivity to planets closer to their stars. Combining micro-
lensing with other techniques provides us with a clearer overall
picture of the planetary content of our Galaxy. From 2007 to 2012,
the Microlensing Observations in Astrophysics (MOA) group, a
collaboration between researchers in Japan and New Zealand, issued
3,300 alerts informing the astronomical community about ongoing
microlensing events. The team identified 1,474 well-observed
microlensing events, with 22 displaying clear planetary signals.
They include four planets that were never previously reported. To
study the events in greater detail, the team included data from the
other major microlensing project operating over the same period, the
Optical Gravitational Lensing Experiment (OGLE), as well as additional
observations from other projects designed to follow up on MOA and OGLE
alerts. From that information, the researchers determined the
frequency of planets as a function of the mass ratio of the planet and
star and the distance between them. For a typical planet-hosting star
with about 60% of the Sun's mass, the typical microlensing planet has
between 10 and 40 times the Earth's mass. For comparison, Neptune in
our own Solar System has a mass equivalent to 17 Earths. The results
imply that cold Neptune-mass worlds are likely to be the most common
types of planets beyond the so-called snow line, the point where water
remained frozen during planetary formation. In the Solar System, the
snow line is thought to have been located at about 2.7 times the
Earth's mean distance from the Sun, placing it in the middle of the
main asteroid belt today.


BIRTHPLACES OF MOST CURRENT STARS
National Radio Astronomy Observatory

Astronomers have used the Very Large Array (VLA) and the Atacama Large
Millimetre Array (ALMA) to look at distant galaxies seen as they were
some 10 thousand million years ago. At that time, the Universe was
experiencing its peak rate of star formation. Most stars in the
present Universe were born then. We knew that galaxies in that era
were forming stars prolifically, but we did not know what those
galaxies looked like, because they were shrouded in so much dust that
almost no visible light escaped them. Radio waves, unlike visible
light, can get through the dust. However, in order to reveal the
details of such distant -- and faint -- galaxies, the astronomers had
to use the most sensitive radio telescopes. The new observations,
from the VLA and ALMA, have answered long-standing questions about the
mechanisms that were responsible for the bulk of star formation in
those galaxies. They found that intense star formation most
frequently occurred throughout the galaxies, whereas in present-day
galaxies with similar high star-formation rates it tends to occur in
much smaller regions. The astronomers used the VLA and ALMA to study
galaxies in the Hubble Ultra-Deep Field, a small area of sky observed
since 2003 with the Hubble Space Telescope (HST). The HST made very
long exposures of the area to detect galaxies in the far-distant
Universe, and numerous observing programmes with other telescopes have
followed up on the HST work. The VLA showed where star formation was
occurring, and ALMA revealed the cold gas that is the fuel for star
formation.


SUPERCLUSTER OF GALAXIES NEAR MILKY WAY
Australian National University

Astronomers have found one of the Universe's biggest superclusters of
galaxies near the Milky Way. The Vela supercluster, which had
previously gone undetected because it was hidden by stars and dust in
the Milky Way, is a huge mass that influenced the motion of our
Galaxy. It is one of the biggest concentrations of galaxies in the
Universe -- possibly the biggest in the neighbourhood of our Galaxy,
but that will need to be confirmed by further study. The gravity of
the Vela supercluster may explain the difference between the measured
motion of the Milky Way through space and the motion predicted from
the distribution of previously mapped galaxies. The team used the
Anglo-Australian Telescope to measure distances for many galaxies to
confirm earlier suggestions that Vela is a supercluster. It also
helped to estimate the supercluster's effect on the motion of the
Milky Way. The research involved astronomers based in South Africa,
Australia and Europe. Two new Australian surveys starting in 2017
will assess the size of the Vela supercluster. The Taipan optical
survey will measure galaxy distances over a bigger area around Vela,
while the WALLABY radio survey will be able to see through the densest
parts of the Milky Way into the supercluster's heart.


LARGEST DIGITAL SURVEY OF VISIBLE UNIVERSE
Queen's University Belfast

The largest-ever digital survey of the visible Universe, mapping
billions of stars and galaxies, has been publicly released.
The data have been made available by the international Pan-STARRS
project, which includes scientists from Queen's University Belfast,
who have claimed that it will lead to new discoveries about the
Universe. Astronomers and cosmologists used a 1.8-m telescope at the
summit of Haleakala, on Maui, Hawaii, to image three-quarters of the
visible sky repeatedly over four years. The Pan-STARRS1 Surveys
include 3 billion separate sources, including stars, galaxies, and
other objects, and are represented by two petabytes of computer data.
Pan-STARRS is hosted by the University of Hawaii Institute for
Astronomy, which is releasing the data alongside the Space Telescope
Science Institute in Baltimore. The international collaboration also
includes Queen's University Belfast and the Universities of Durham and
Edinburgh, and is supported by NASA and the NSF. The project has
found nearby asteroids in our Solar System, and also the most luminous
distant explosions in the Universe. Pan-STARRS has already made
discoveries from Near Earth Objects and Kuiper-Belt objects in the
Solar System to lonely planets between the stars; it has mapped the
dust in three dimensions in our Galaxy and found new streams of stars;
and it has found new kinds of exploding stars and distant quasars in
the early Universe. The roll-out of the survey data is being done in
two steps. The current release is the 'Static Sky' which provides an
average value for the position, brightness and colour for objects seen
in the sky at individual moments in time. In 2017, a second set of
data will be released including catalogues and images from each of the
individual snapshots that Pan-STARRS took of a given region of sky.
The data from the Pan-STARRS1 surveys will be available online at
panstarrs.stsci.edu .

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Clive

MARS ICE DEPOSIT HOLDS AS MUCH WATER AS LAKE SUPERIOR
NASA/Jet Propulsion Laboratory

Researchers using the Mars Reconnaissance Orbiter have discovered
that, frozen beneath a region of cracked and pitted plains on Mars,
lies about as much water as is contained in Lake Superior, largest of
the North-American Great Lakes. Scientists examined part of Mars'
Utopia Planitia region, in the mid-northern latitudes, with the
orbiter's ground-penetrating Shallow Radar (SHARAD) instrument.
Utopia Planitia is a basin with a diameter of about 3,300 km,
resulting from a major impact early in Mars' history and subsequently
filled. Analyses of the radar data from more than 600 overhead passes
reveal an ice deposit more extensive in area than the British Isles.
The deposit ranges in thickness from about 80 to 170 metres, with a
composition that is 50 to 85% water ice, mixed with dust or larger
rocky particles. At the latitude of the deposit -- about 45 degrees
-- ice cannot persist on the surface of Mars today; it sublimes into
water vapour in the thin, dry atmosphere. The Utopia deposit is
shielded from the atmosphere by a covering of soil, estimated to be
about 1 to 10 metres thick. Mars today, with an axial tilt of 25
degrees, accumulates large amounts of water ice at the poles. In
cycles lasting about 120,000 years, the tilt varies to nearly twice
that much, warming the poles and driving ice to middle latitudes.
Climate modelling and previous findings of buried mid-latitude ice
indicate that frozen water accumulates away from the poles during the
long high-tilt periods.

The newly surveyed ice deposit spans latitudes from 39 to 49 degrees
within the plains. It represents less than 1% of all known water
ice on Mars, but it more than doubles the volume of thick, buried
ice sheets known in the northern plains. Ice deposits close to the
surface are being considered as a resource for potential astronauts.
The deposit described here is probably more accessible than most water
ice on Mars, because it is at a relatively low latitude and it lies in
a flat, smooth area where landing a spacecraft would be less hazardous
than in some of the other areas where there is buried ice. The
Utopian water is all frozen now. If there were a melted layer --
which would be significant for the possibility of life on Mars -- it
would have been evident in the radar scans. However, some melting can
not be ruled out during different climate conditions when the planet's
axis was more tilted.

NEW FAMILY OF STARS IN CORE OF MILKY WAY
Liverpool John Moores University

Astronomers have discovered a new family of stars in the core of our
Milky Way galaxy, providing new insights into the early stages of the
Galaxy's formation. The discovery, made from the Sloan Digital Sky
Survey, has shed new light on the origins of globular clusters. One
of the projects of this collaboration is APOGEE (the Apache Point
Observatory Galactic Evolution Experiment), which collects infrared
data for hundreds of thousands of stars in the Milky Way. It was
through observing stars in the infrared towards the Galactic Centre
that the discovery was made of a new population of stars, the like
of which had been seen before only inside globular clusters. That
intriguing new family of stars could possibly have belonged to
globular clusters that were destroyed during the violent initial
formation of the Galactic centre, in which case there would have been
about 10 times more globular clusters in the Milky Way in its early
stages than there are today. That could mean that a substantial
fraction of the old stars inhabiting the inner parts of the Galaxy
today may have been formed initially in globular clusters that were
later destroyed.

The finding helps astronomers address fascinating questions such as
what is the nature of the stars in the inner regions of the Milky Way,
how globular clusters formed, and what role they played in the
formation of the early Milky Way -- and by extension the formation of
other galaxies. The centre of the Milky Way is poorly understood,
because it is blocked from view by intervening dust. Observing in the
infrared, which is less absorbed by dust than visible light, APOGEE
can see the centre of the Galaxy better than other methods. From the
observations the chemical compositions of thousands of stars could be
determined; among them was a considerable number of stars that
differed from the bulk of those in the inner regions of the Galaxy,
owing to their very high abundance of nitrogen. While not certain, it
is suspected that those stars resulted from the destruction of
globular clusters. They could also be the by-products of the first
episodes of star formation taking place at the beginning of the
Galaxy's history.


EXTREMELY FAINT SATELLITE GALAXY OF MILKY WAY
National Astronomical Observatory of Japan

Astronomers have found an extremely faint dwarf satellite galaxy of
the Milky Way. The satellite lies in the direction of the constellation
Virgo and has accordingly been named Virgo I. At an absolute
magnitude of -0.8 in the optical waveband, it may well be the faintest
satellite galaxy yet found. Its discovery suggests the presence of a
large number of yet-undetected dwarf satellites in the halo of the
Milky Way, and provides important insights into galaxy formation
through hierarchical assembly of dark matter. Currently, some 50
satellite galaxies of the Milky Way have been identified. About 40
of them are faint and diffuse and belong to the category of 'dwarf
spheroidal galaxies'. Many recently discovered dwarf galaxies,
especially those found in systematic photometric surveys such as the
Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey (DES), are
very faint, with absolute luminosities in the optical waveband less
than -8 magnitude. They are called 'ultra-faint dwarf galaxies'.
However, previous searches made use of telescopes of apertures 2.5 to
4 metres, so only satellites relatively close to the Sun or those with
brighter magnitudes were identified.

The combination of the large aperture of the 8.2-m Subaru Telescope
and the large field of view of the Hyper Suprime Cam (HSC) instrument
is very powerful for this study. It enables an efficient search to
be made for very faint dwarf satellites over large areas of the sky.
The first step in searching for a new dwarf galaxy is to identify an
over-density of stars in the sky, using photometric data. Next is to
assess that the over-dense appearance is not due to line-of-sight or
accidental juxtapositions of unrelated dense fields, but is really a
stellar system. The standard method for doing that is to look for a
characteristic distribution of stars in the colour-magnitude diagram
(analogous to the Hertzsprung-Russell diagram). Stars in a general
field show no particular patterns in this diagram. The team examined
the early data of the Subaru Strategic Survey with HSC and found an
apparent over-density of stars in Virgo with very high statistical
significance, showing a characteristic pattern of an ancient stellar
system in the colour-magnitude diagram. It is indeed a galaxy,
because it is spatially extended with a radius of 124 light-years --
larger than a globular cluster with comparable luminosity. The
faintest dwarf satellites identified so far are Segue I, discovered by
SDSS (-1.5 mag) and Cetus II in DES (0.0 mag). Cetus II is yet to be
confirmed, as it is too compact as a galaxy, so Virgo I may turn out
to be the faintest one so far discovered. It lies at a distance of
280,000 light-years from the Sun, and such a remote galaxy with such a
low luminosity has not been identified in previous surveys. It is
beyond the reach of SDSS, which has previously surveyed the same area
in the direction of the constellation Virgo.


DO EXTREMELY REDDENED QUASARS EXTINGUISH STAR FORMATION?
University of California - Riverside

Galaxies formed and grew thousands of millions of years ago by
accumulating gas from their surroundings, or colliding and merging
with other young galaxies. Those early stages of galaxy assembly are
believed to be accompanied by episodes of rapid star formation, known
as starbursts, and rapid growth of a single super-massive black hole
in each galactic centre. A popular paradigm for such evolution has
the black holes growing mostly in obscurity, buried deep within the
dusty gas in the centres of the galaxies. Those are rich star-forming
galaxies, until a blowout of gas and dust (outflow) extinguishes the
star formation and halts further growth in the black holes. At that
stage there is revealed the luminous material in the immediate
vicinity of the rapidly growing black hole in the galactic nucleus.
Such objects are known as quasars. Quasars can eject material at
high speeds, possibly helping to drive the blowout and regulate star
formation in their host galaxies. However, many aspects of that
evolutionary scheme are not understood. Quasars that are partially
obscured by dust, which reddens their light in a way that is similar
to the apparent reddening of the Sun as it approaches sunset on
Earth, might provide windows into galactic evolution during the brief
transition stage when the starburst is winding down and the visibly
luminous quasar is first being revealed in the galactic centre. New
research describes the discovery of the new population of extremely
red quasars detected in the Baryon Oscillation Sky Survey (BOSS) of
the Sloan Digital Sky Survey (SDSS).

The main goal of that study was to determine the size of the
population of extremely red quasars, and to characterize its basic
properties in comparison with the much larger population of quasars
in the BOSS--SDSS survey overall. The extremely red quasars were
selected for study because of their extreme colour, but the analysis
reveal a number of peculiar properties consistent with a unique and
possibly young evolutionary stage. In particular, they have an
exceptionally high incidence of powerful quasar-driven outflows that
could be involved in galaxy-wide blowouts of gas and dust. Overall,
the gaseous environments around the black holes appear to be more
extended and more energetic than the environments of normal quasars,
which might occur at specific times when young gas-rich host galaxies
are dumping prodigious amounts of matter into the central black holes,
creating an extreme variety of quasars. More work is needed now to
examine the population of extremely red quasars further and understand
its relationship to the general phenomenon of quasars and, perhaps, to
a particularly violent phase of quasar-galaxy evolution.


LARGE NUMBER OF DWARF GALAXES FOUND IN EARLY UNIVERSE
University of California at Riverside

A team of researchers has found a large population of distant dwarf
galaxies that could reveal important details about a productive period
of star formation in the Universe thousands of millions of years ago.
The findings build on a growing body of knowledge about dwarf
galaxies, the smallest and dimmest galaxies in the Universe. Though
relatively diminutive, they are very important for understanding the
history of the Universe. It is believed that dwarf galaxies played a
significant role during the 're-ionization era', in transforming the
early Universe from being dark, neutral and opaque to one that is
bright, ionized and transparent. Despite their importance, distant
dwarf galaxies remain elusive, because they are extremely faint and
mostly beyond the reach of even the best telescopes, so the current
picture of the early Universe is incomplete. However, gravitational
lensing, which was predicted by Einstein from his general theory of
relativity long before it was actually observed, causes a massive
object such as a galaxy located along the line of sight to another
distant object to act as a natural lens, concentrating the light
coming from the background source. The phenomenon sometimes allows
us to discover distant dwarf galaxies that would otherwise be too
faint to detect.

As a proof of concept, in 2014 the team targeted one cluster of
galaxies that produces the gravitational-lensing effect and got a
glimpse of what appeared to be a large population of distant dwarf
galaxies. The team used the Wide-Field Camera 3 on the Hubble Space
Telescope to take deep images of three clusters of galaxies. They
found the large population of distant dwarf galaxies from a time when
the Universe was between two and six thousand million years old.
That cosmic time is critical, as it was the most productive time
for star formation in the Universe. In addition, the team obtained
spectroscopic data from the Multi-Object Spectrograph for Infrared
Exploration (MOSFIRE) on the Keck telescope, and confirmed that the
galaxies belonged to that important cosmic period. Those dwarf
galaxies are 10 to 100 times fainter than galaxies that had been
previously observed from that period of time. Though faint, the
galaxies are far more numerous than their brighter counterparts.

The study demonstrates that the number of dwarf galaxies changed
during that important time period in such a way that they were
even more abundant at earlier times. In fact, the researchers had
unveiled a population of dwarf galaxies that were the most numerous
galaxies in the Universe during those times. Despite their individual
faintness, the dwarf galaxies produced more than half of all ultra-
violet light during that era. As ultraviolet radiation is produced
by young hot stars, dwarf galaxies evidently hosted a significant
fraction of newly-formed stars at that period of cosmic time. Those
results suggest that dwarf galaxies played a prominent role in the
re-ionization era; they will be among the primary targets of the next
generation of telescopes, particularly the James Webb Space Telescope,
scheduled to be launched in 2018.


MARS PROBE RETURNS FIRST PICTURES
BBC Online

Europe's and Russia's new satellite at Mars has sent back its first
images of the planet. The Trace Gas Orbiter (TGO) arrived on October
19, putting itself into a highly eccentric elliptical parking orbit,
which must be circularized over the coming year before the mission
can become fully operational. Scientists have, however, taken the
opportunity of some close passes to the planet in recent days to check
out the TGO's instrumentation. They are delighted at the quality of
the pictures returned from the camera system, CaSSIS (the Colour and
Stereo Surface Imaging System). Two of TGO's sensors - NOMAD and ACS
- also came through their early tests. Those are the sensors that
will make a detailed inventory of Mars' atmospheric gases. In
particular, they will go after the components that constitute less
than 1% of the planet's air -- chemical species such as methane, water
vapour, nitrogen dioxide, and sulphur dioxide. Methane is the main
focus. From previous measurements, its concentration seems to be low
and sporadic in nature, but the mere fact that it is detected at all
is really fascinating.

Methane (CH4) is the simplest organic molecule, and ought to be
destroyed easily in the harsh Martian environment, so its persistence
-- and the occasional spikes in its signal -- indicate a source that
replenishes the gas. The speculation is that it could be coming from
microbial life somewhere on the planet. It will be CaSSIS's job to
look for possible topographical forms on the surface that might tie
into methane sources. A fourth instrument, FREND, will sense hydrogen
in the near-surface. Those data can be used as proxy for the presence
of water or hydrated minerals. That again is information that could
yield answers to the methane question. TGO was the unspoken success
on the day that ESA's Schiaparelli lander crashed onto Mars. The
surface probe had been dropped off by TGO and was making its ill-fated
descent just as the satellite took up its parking orbit, and the
successful insertion went almost unnoticed in the fuss over
Schiaparelli. TGO is the first phase in a joint venture at Mars that
Europe is undertaking with Russia. The second step in the project,
known as ExoMars, is to put a robot rover on the planet in 2021. It
needs a lot of money from the European side to go forward, however --
just over 400m Euros. Research ministers from ESA member states are
meeting this week in Switzerland to try to resolve the budget problem.

ENB 435

Clive

MARS ICE DEPOSIT HOLDS AS MUCH WATER AS LAKE SUPERIOR
NASA/Jet Propulsion Laboratory

Researchers using the Mars Reconnaissance Orbiter have discovered
that, frozen beneath a region of cracked and pitted plains on Mars,
lies about as much water as is contained in Lake Superior, largest of
the North-American Great Lakes. Scientists examined part of Mars'
Utopia Planitia region, in the mid-northern latitudes, with the
orbiter's ground-penetrating Shallow Radar (SHARAD) instrument.
Utopia Planitia is a basin with a diameter of about 3,300 km,
resulting from a major impact early in Mars' history and subsequently
filled. Analyses of the radar data from more than 600 overhead passes
reveal an ice deposit more extensive in area than the British Isles.
The deposit ranges in thickness from about 80 to 170 metres, with a
composition that is 50 to 85% water ice, mixed with dust or larger
rocky particles. At the latitude of the deposit -- about 45 degrees
-- ice cannot persist on the surface of Mars today; it sublimes into
water vapour in the thin, dry atmosphere. The Utopia deposit is
shielded from the atmosphere by a covering of soil, estimated to be
about 1 to 10 metres thick. Mars today, with an axial tilt of 25
degrees, accumulates large amounts of water ice at the poles. In
cycles lasting about 120,000 years, the tilt varies to nearly twice
that much, warming the poles and driving ice to middle latitudes.
Climate modelling and previous findings of buried mid-latitude ice
indicate that frozen water accumulates away from the poles during the
long high-tilt periods.

The newly surveyed ice deposit spans latitudes from 39 to 49 degrees
within the plains. It represents less than 1% of all known water
ice on Mars, but it more than doubles the volume of thick, buried
ice sheets known in the northern plains. Ice deposits close to the
surface are being considered as a resource for potential astronauts.
The deposit described here is probably more accessible than most water
ice on Mars, because it is at a relatively low latitude and it lies in
a flat, smooth area where landing a spacecraft would be less hazardous
than in some of the other areas where there is buried ice. The
Utopian water is all frozen now. If there were a melted layer --
which would be significant for the possibility of life on Mars -- it
would have been evident in the radar scans. However, some melting can
not be ruled out during different climate conditions when the planet's
axis was more tilted.


NEW FAMILY OF STARS IN CORE OF MILKY WAY
Liverpool John Moores University

Astronomers have discovered a new family of stars in the core of our
Milky Way galaxy, providing new insights into the early stages of the
Galaxy's formation. The discovery, made from the Sloan Digital Sky
Survey, has shed new light on the origins of globular clusters. One
of the projects of this collaboration is APOGEE (the Apache Point
Observatory Galactic Evolution Experiment), which collects infrared
data for hundreds of thousands of stars in the Milky Way. It was
through observing stars in the infrared towards the Galactic Centre
that the discovery was made of a new population of stars, the like
of which had been seen before only inside globular clusters. That
intriguing new family of stars could possibly have belonged to
globular clusters that were destroyed during the violent initial
formation of the Galactic centre, in which case there would have been
about 10 times more globular clusters in the Milky Way in its early
stages than there are today. That could mean that a substantial
fraction of the old stars inhabiting the inner parts of the Galaxy
today may have been formed initially in globular clusters that were
later destroyed.

The finding helps astronomers address fascinating questions such as
what is the nature of the stars in the inner regions of the Milky Way,
how globular clusters formed, and what role they played in the
formation of the early Milky Way -- and by extension the formation of
other galaxies. The centre of the Milky Way is poorly understood,
because it is blocked from view by intervening dust. Observing in the
infrared, which is less absorbed by dust than visible light, APOGEE
can see the centre of the Galaxy better than other methods. From the
observations the chemical compositions of thousands of stars could be
determined; among them was a considerable number of stars that
differed from the bulk of those in the inner regions of the Galaxy,
owing to their very high abundance of nitrogen. While not certain, it
is suspected that those stars resulted from the destruction of
globular clusters. They could also be the by-products of the first
episodes of star formation taking place at the beginning of the
Galaxy's history.


EXTREMELY FAINT SATELLITE GALAXY OF MILKY WAY
National Astronomical Observatory of Japan

Astronomers have found an extremely faint dwarf satellite galaxy of
the Milky Way. The satellite lies in the direction of the constellation
Virgo and has accordingly been named Virgo I. At an absolute
magnitude of -0.8 in the optical waveband, it may well be the faintest
satellite galaxy yet found. Its discovery suggests the presence of a
large number of yet-undetected dwarf satellites in the halo of the
Milky Way, and provides important insights into galaxy formation
through hierarchical assembly of dark matter. Currently, some 50
satellite galaxies of the Milky Way have been identified. About 40
of them are faint and diffuse and belong to the category of 'dwarf
spheroidal galaxies'. Many recently discovered dwarf galaxies,
especially those found in systematic photometric surveys such as the
Sloan Digital Sky Survey (SDSS) and the Dark Energy Survey (DES), are
very faint, with absolute luminosities in the optical waveband less
than -8 magnitude. They are called 'ultra-faint dwarf galaxies'.
However, previous searches made use of telescopes of apertures 2.5 to
4 metres, so only satellites relatively close to the Sun or those with
brighter magnitudes were identified.

The combination of the large aperture of the 8.2-m Subaru Telescope
and the large field of view of the Hyper Suprime Cam (HSC) instrument
is very powerful for this study. It enables an efficient search to
be made for very faint dwarf satellites over large areas of the sky.
The first step in searching for a new dwarf galaxy is to identify an
over-density of stars in the sky, using photometric data. Next is to
assess that the over-dense appearance is not due to line-of-sight or
accidental juxtapositions of unrelated dense fields, but is really a
stellar system. The standard method for doing that is to look for a
characteristic distribution of stars in the colour-magnitude diagram
(analogous to the Hertzsprung-Russell diagram). Stars in a general
field show no particular patterns in this diagram. The team examined
the early data of the Subaru Strategic Survey with HSC and found an
apparent over-density of stars in Virgo with very high statistical
significance, showing a characteristic pattern of an ancient stellar
system in the colour-magnitude diagram. It is indeed a galaxy,
because it is spatially extended with a radius of 124 light-years --
larger than a globular cluster with comparable luminosity. The
faintest dwarf satellites identified so far are Segue I, discovered by
SDSS (-1.5 mag) and Cetus II in DES (0.0 mag). Cetus II is yet to be
confirmed, as it is too compact as a galaxy, so Virgo I may turn out
to be the faintest one so far discovered. It lies at a distance of
280,000 light-years from the Sun, and such a remote galaxy with such a
low luminosity has not been identified in previous surveys. It is
beyond the reach of SDSS, which has previously surveyed the same area
in the direction of the constellation Virgo.


DO EXTREMELY REDDENED QUASARS EXTINGUISH STAR FORMATION?
University of California - Riverside

Galaxies formed and grew thousands of millions of years ago by
accumulating gas from their surroundings, or colliding and merging
with other young galaxies. Those early stages of galaxy assembly are
believed to be accompanied by episodes of rapid star formation, known
as starbursts, and rapid growth of a single super-massive black hole
in each galactic centre. A popular paradigm for such evolution has
the black holes growing mostly in obscurity, buried deep within the
dusty gas in the centres of the galaxies. Those are rich star-forming
galaxies, until a blowout of gas and dust (outflow) extinguishes the
star formation and halts further growth in the black holes. At that
stage there is revealed the luminous material in the immediate
vicinity of the rapidly growing black hole in the galactic nucleus.
Such objects are known as quasars. Quasars can eject material at
high speeds, possibly helping to drive the blowout and regulate star
formation in their host galaxies. However, many aspects of that
evolutionary scheme are not understood. Quasars that are partially
obscured by dust, which reddens their light in a way that is similar
to the apparent reddening of the Sun as it approaches sunset on
Earth, might provide windows into galactic evolution during the brief
transition stage when the starburst is winding down and the visibly
luminous quasar is first being revealed in the galactic centre. New
research describes the discovery of the new population of extremely
red quasars detected in the Baryon Oscillation Sky Survey (BOSS) of
the Sloan Digital Sky Survey (SDSS).

The main goal of that study was to determine the size of the
population of extremely red quasars, and to characterize its basic
properties in comparison with the much larger population of quasars
in the BOSS--SDSS survey overall. The extremely red quasars were
selected for study because of their extreme colour, but the analysis
reveal a number of peculiar properties consistent with a unique and
possibly young evolutionary stage. In particular, they have an
exceptionally high incidence of powerful quasar-driven outflows that
could be involved in galaxy-wide blowouts of gas and dust. Overall,
the gaseous environments around the black holes appear to be more
extended and more energetic than the environments of normal quasars,
which might occur at specific times when young gas-rich host galaxies
are dumping prodigious amounts of matter into the central black holes,
creating an extreme variety of quasars. More work is needed now to
examine the population of extremely red quasars further and understand
its relationship to the general phenomenon of quasars and, perhaps, to
a particularly violent phase of quasar-galaxy evolution.


LARGE NUMBER OF DWARF GALAXES FOUND IN EARLY UNIVERSE
University of California at Riverside

A team of researchers has found a large population of distant dwarf
galaxies that could reveal important details about a productive period
of star formation in the Universe thousands of millions of years ago.
The findings build on a growing body of knowledge about dwarf
galaxies, the smallest and dimmest galaxies in the Universe. Though
relatively diminutive, they are very important for understanding the
history of the Universe. It is believed that dwarf galaxies played a
significant role during the 're-ionization era', in transforming the
early Universe from being dark, neutral and opaque to one that is
bright, ionized and transparent. Despite their importance, distant
dwarf galaxies remain elusive, because they are extremely faint and
mostly beyond the reach of even the best telescopes, so the current
picture of the early Universe is incomplete. However, gravitational
lensing, which was predicted by Einstein from his general theory of
relativity long before it was actually observed, causes a massive
object such as a galaxy located along the line of sight to another
distant object to act as a natural lens, concentrating the light
coming from the background source. The phenomenon sometimes allows
us to discover distant dwarf galaxies that would otherwise be too
faint to detect.

As a proof of concept, in 2014 the team targeted one cluster of
galaxies that produces the gravitational-lensing effect and got a
glimpse of what appeared to be a large population of distant dwarf
galaxies. The team used the Wide-Field Camera 3 on the Hubble Space
Telescope to take deep images of three clusters of galaxies. They
found the large population of distant dwarf galaxies from a time when
the Universe was between two and six thousand million years old.
That cosmic time is critical, as it was the most productive time
for star formation in the Universe. In addition, the team obtained
spectroscopic data from the Multi-Object Spectrograph for Infrared
Exploration (MOSFIRE) on the Keck telescope, and confirmed that the
galaxies belonged to that important cosmic period. Those dwarf
galaxies are 10 to 100 times fainter than galaxies that had been
previously observed from that period of time. Though faint, the
galaxies are far more numerous than their brighter counterparts.

The study demonstrates that the number of dwarf galaxies changed
during that important time period in such a way that they were
even more abundant at earlier times. In fact, the researchers had
unveiled a population of dwarf galaxies that were the most numerous
galaxies in the Universe during those times. Despite their individual
faintness, the dwarf galaxies produced more than half of all ultra-
violet light during that era. As ultraviolet radiation is produced
by young hot stars, dwarf galaxies evidently hosted a significant
fraction of newly-formed stars at that period of cosmic time. Those
results suggest that dwarf galaxies played a prominent role in the
re-ionization era; they will be among the primary targets of the next
generation of telescopes, particularly the James Webb Space Telescope,
scheduled to be launched in 2018.


MARS PROBE RETURNS FIRST PICTURES
BBC Online

Europe's and Russia's new satellite at Mars has sent back its first
images of the planet. The Trace Gas Orbiter (TGO) arrived on October
19, putting itself into a highly eccentric elliptical parking orbit,
which must be circularized over the coming year before the mission
can become fully operational. Scientists have, however, taken the
opportunity of some close passes to the planet in recent days to check
out the TGO's instrumentation. They are delighted at the quality of
the pictures returned from the camera system, CaSSIS (the Colour and
Stereo Surface Imaging System). Two of TGO's sensors - NOMAD and ACS
- also came through their early tests. Those are the sensors that
will make a detailed inventory of Mars' atmospheric gases. In
particular, they will go after the components that constitute less
than 1% of the planet's air -- chemical species such as methane, water
vapour, nitrogen dioxide, and sulphur dioxide. Methane is the main
focus. From previous measurements, its concentration seems to be low
and sporadic in nature, but the mere fact that it is detected at all
is really fascinating.

Methane (CH4) is the simplest organic molecule, and ought to be
destroyed easily in the harsh Martian environment, so its persistence
-- and the occasional spikes in its signal -- indicate a source that
replenishes the gas. The speculation is that it could be coming from
microbial life somewhere on the planet. It will be CaSSIS's job to
look for possible topographical forms on the surface that might tie
into methane sources. A fourth instrument, FREND, will sense hydrogen
in the near-surface. Those data can be used as proxy for the presence
of water or hydrated minerals. That again is information that could
yield answers to the methane question. TGO was the unspoken success
on the day that ESA's Schiaparelli lander crashed onto Mars. The
surface probe had been dropped off by TGO and was making its ill-fated
descent just as the satellite took up its parking orbit, and the
successful insertion went almost unnoticed in the fuss over
Schiaparelli. TGO is the first phase in a joint venture at Mars that
Europe is undertaking with Russia. The second step in the project,
known as ExoMars, is to put a robot rover on the planet in 2021. It
needs a lot of money from the European side to go forward, however --
just over 400m Euros. Research ministers from ESA member states are
meeting this week in Switzerland to try to resolve the budget problem.