Topic: Mid October Astronomy Bulletin

[Clive]

CURIOSITY FINDS WATER ON MARS
NASA

Curiosity landed in Gale Crater on the surface of Mars on 2012 Aug. 6.
There was hope that it could throw light on the question: "Could Mars
have once harboured life?"  To do that, Curiosity carried equipment
(grandiosely entitled the 'Sample Analysis at Mars (SAM) instrument
suite'), which includes a gas chromatograph, a mass spectrometer and
a tuneable laser spectrometer) for gathering and processing samples of
rock and soil.  Those tools enable SAM to identify a wide range of
chemical compounds and determine the ratios of different isotopes of
key elements.  By combining analyses of water and other volatiles from
SAM with mineralogical, chemical and areological data from Curiosity's
other instruments, we have made some progress in understanding surface
processes and the action of water on Mars.  Operators used the rover's
scoop to shovel up dust, dirt and finely grained soil from a sandy
patch.  They fed portions of the fifth scoop into SAM, where the
'fines' -- dust, dirt and fine soil -- were heated to 835C.  Baking
the sample also indicated a compound containing chlorine and oxygen,
probably chlorate or perchlorate such as had previously found near the
north pole on Mars.  Finding such compounds also at Curiosity's
equatorial site suggests that they might be distributed more globally.
The analysis also suggests the presence of carbonate materials, which
form in the presence of water.

In addition to determining the amount of the major gases released, SAM
also analyzed ratios of isotopes of hydrogen and carbon in the
released water and carbon dioxide.  Isotopes are variants of the same
chemical element (so with the same numbers of protons in the nuclei)
with different numbers of neutrons, and therefore different atomic
weights.  SAM found that the ratio of some isotopes in the soil is
similar to the ratio found in atmospheric samples analyzed earlier,
indicating that the surface soil has interacted heavily with the
atmosphere.  The isotopic ratios, including hydrogen-to-deuterium
ratios and carbon isotopes, tend to support the idea that as the dust
is moved around the planet, it reacts with some of the gases from the
atmosphere.  SAM can also search for trace levels of organic
compounds.  Although several simple organic compounds were detected in
the experiments, they are not clearly Martian in origin.  Instead, it
is likely that they formed during the high-temperature experiments,
when the heat decomposed perchlorates in the samples, releasing oxygen
and chlorine that then reacted with terrestrial organics already
present in the SAM instrument.  SAM can perform another kind of
experiment to address the question of whether organic molecules are
present in the Martian samples.  The SAM suite includes nine fluid-
filled cups which hold chemicals that can react with organic molecules
if such are present in the soil samples.  The combined results could
shed light on the composition of the planet's surface, and may offer
direction for future research.


FOMALHAUT IS A TRIPLE STAR
University of Rochester.

The 'nearby' star system Fomalhaut -- of special interest for its
unusual exoplanet and dusty debris disc -- has been discovered to be
not just a double star, as astronomers had thought, but one of the
widest triple stars known.  By carefully analyzing astrometric
(precise movements) and spectroscopic measurements (that allow the
temperature and radial velocity to be determined), researchers were
able to measure the distance and motion of the third star.  They
concluded that the star, until recently known as LP 876-10, is part of
the Fomalhaut system, making it Fomalhaut C.  Fomalhaut C appears a
long way from the big, bright star that is Fomalhaut A.  The stars are
about 5.5 degrees apart, which goes a long way towards explaining why
the connection between LP 876-10 and Fomalhaut had previously been
overlooked; the high-quality astrometric and velocity data were the
key.  The researchers also needed to show that it would be feasible
for the two stars to be gravitationally bound together, rather than
moving independently.  Fomalhaut A is such a massive star, about twice
the mass of our Sun, that it can keep its tiny companion bound to it.
despite their separation of 158,000 astronomical units (Earth--Sun
distances).  The team had already gathered several years of
observations on the companion star with the SMARTS 0.9-m telescope at
Cerro Tololo in Chile.  The radial velocity of the star was measured
by observers from the University of Chicago and proved to be within
about 1 km/s of that of Fomalhaut A.

There are 11 star systems closer to us than Fomalhaut that consist of
three or more stars, including the closest star system of all, Alpha
Centauri.  The new measurements show that the Fomalhaut system is the
most massive and widest among these 'nearby' multiple systems.
Fomalhaut A is the 18th-brightest star, and is one of the few stars
that have both a directly-imaged exo-planet and a dusty debris disc,
but it was only recently confirmed that Fomalhaut was a binary star
although that had first been suggested in the 1890s.  Many questions
remain about Fomalhaut A's exo-planet and debris disc, such as why the
planet is in such an eccentric orbit and why the debris disc does not
appear to be centred on the star A.  It is possible that Fomalhaut's
wide companions B and C have perturbed the planet and debris belt
orbiting A; however, the orbits of the companion stars are not
well-constrained -- the orbits of B and C around A probably take
millions of years, so they cannot be determined accurately at all
soon.  While C is a red-dwarf star -- the most common type in the
Universe -- B is an orange-dwarf star about 3/4 the mass of the Sun.
From the vantage point of a hypothetical planet orbiting C, A would
appear to be a brilliant white star about as bright as Venus appears
to us.  B would appear to be an otherwise unremarkable bright orangish
star similar in brightness to Polaris.  The age of the trio is about
440 million years -- roughly a tenth of the age of the Solar System.


FIRST CLOUD MAP OF EXO-PLANET
NASA

Astronomers using data from the Kepler and Spitzer space telescopes
have created the first cloud map of a planet beyond our Solar System,
a Jupiter-like object known as Kepler-7b.  The planet has high clouds
in the west and clear skies in the east.  Previous studies from
Spitzer have resulted in temperature maps of planets orbiting other
stars, but this is the first look at cloud structures.  After
observing for three years, astronomers were able to produce a
very-low-resolution 'map' of the giant, gaseous planet.  They would
not expect to see oceans or continents on such a planet, but they
interpreted the observations in terms of clouds.  Visible-light
observations of Kepler-7b's moon-like phases led to a rough map of the
planet that showed a bright spot on its western hemisphere, but they
were not enough on their own to decipher whether the bright spot was
coming from clouds or heat.  However, the Spitzer space telescope,
observing in the infrared, was able to measure Kepler-7b's
temperature, estimating it to be between 1,100 and 1,300 Kelvin.  That
is relatively cool for a planet that orbits so close to its star --
within 0.06 AU -- and was considered by the astronomers to be too cool
to be the source of light that Kepler observed.  Instead, they think
it was light from the star, refelcted from cloud tops on the west side
of the planet.  Kepler-7b reflects much more light than most giant
planets so far discovered, and astronomers attribute that to clouds in
the upper atmosphere.  The cloud patterns on the planet do not seem to
change much over time -- it has a remarkably stable climate.  The
findings are an early step towards using similar techniques to study
the atmospheres of planets more like the Earth in composition and size.


ASTRONOMERS DISCOVER DENSEST GALAXY
Michigan State University

An international team of astronomers has found a galaxy so dense that
as many as 10,000 stars are crammed into the space of 4 light-years or
the distance between the Sun and Alpha Centauri.  That galaxy is more
massive than any ultra-compact dwarfs of comparable size and is
arguably the densest galaxy known in the local Universe.  It is in the
Virgo cluster of galaxies, about 54 million light years away.  What
makes the galaxy, called M60-UCD1, so remarkable is that about half of
its mass is found within a radius of only about 80 light-years.
making the density of stars about 15,000 times greater than found in
our neighbourhood in the Milky Way.  Another intriguing aspect of the
galaxy is the presence of a bright X-ray source in its centre,
possibly a black hole 10 million times the mass of our Sun.  The
discovery of ultra-compact galaxies is relatively new -- only within
the past 10 years or so.  Until then, astronomers could see such
objects but assumed that they were either single stars or very-distant
galaxies.

Astronomers are trying to determine if M60-UCD1 and other ultra-compact
dwarf galaxies are either born as really jam-packed star clusters or
if they are galaxies that get smaller because they have stars ripped
away from them.  The possible massive black hole, combined with the
high galaxy mass and Sun-like levels of elements found in the stars,
favour the latter idea.  A giant black hole at the centre of M60-UCD1
helps tip the scales against the picture in which that galaxy was once
a star cluster, since such large black holes are not found in such
objects.


FINAL ANTENNA DELIVERED TO ALMA
ESO

The 66th and final antenna for the Atacama Large Millimetre/sub-
millimetre Array (ALMA) project has been handed over.  The 12-m-
diameter dish was manufactured by the European AEM Consortium and also
marks the successful delivery of a total of 25 European antennae --
the largest ESO contract so far.  North America has provided 25 12-m
antennae, while East Asia has delivered 16 (four 12-m and twelve 7-m).
By the end of 2013, all 66 dishes are expected to be working together
as one telescope, in an array that will stretch for up to 16
kilometres across the Chajnantor Plateau in the Atacama Desert of
northern Chile.  Radiation at the wavelengths observed by ALMA comes
from some of the coldest, but also from some of the most distant,
objects, including cold clouds of gas and dust where new stars are
being born, and remote galaxies towards the edge of the observable
Universe.  The Universe is relatively unexplored at sub-millimetre
wavelengths, as the telescopes need extremely dry atmospheric
conditions, many large antennae and advanced detectors.  Even before
completion ALMA has already been used extensively for scientific
projects and has shown great potential.


PROPYLENE FOUND IN SPACE
NASA

The Cassini spacecraft has detected propylene, a chemical used to make
food-storage containers, car bumpers and other products, on Saturn's
moon Titan.  This is the first definitive detection of propylene
otherwise than on Earth.  A small amount of propylene was identified
in Titan's lower atmosphere by Cassini's 'Composite Infrared
Spectrometer' (CIRS).  That instrument measures the infrared light, or
heat radiation, emitted from Saturn and its moons in much the same way
our hands feel the warmth of a fire.  Propylene is the first molecule
to be discovered on Titan by CIRS.  By isolating the same signal at
various altitudes within the lower atmosphere, researchers identified
the chemical with a high degree of confidence.  CIRS can identify a
particular gas glowing in the lower layers of the atmosphere from its
unique thermal fingerprint.  The challenge is to isolate the one
signature from the signals of all other gases around it.

Voyager 1, which flew past Titan in 1980, identified many of the gases
in Titan's hazy brownish atmosphere as hydrocarbons, the chemicals
that primarily make up petroleum and other fossil fuels on Earth.
On Titan, hydrocarbons form after sunlight breaks apart methane, the
second-most plentiful gas in that atmosphere.  The newly freed
fragments can link up to form chains with two, three or more carbon
atoms.  The family of chemicals with two carbon atoms includes the
inflammable gas ethane.  Propane, a common fuel for portable stoves,
belongs to the three-carbon family.  Voyager detected all members of
the one- and two-carbon families in Titan's atmosphere.  From the
three-carbon family, the spacecraft found propane, the heaviest
member, and propyne, one of the lightest members.  But the middle
chemicals, one of which is propylene, were missing.  As researchers
continued to discover more and more chemicals in Titan's atmosphere
with ground- and space-based instruments, propylene was one that
remained elusive.  It was finally found as a result of more careful
analysis of the CIRS data.


SPACECRAFT GOES INTO LUNAR ORBIT
Spaceweather.com

Among the few people allowed to work during the US government
shutdown, controllers for NASA's 'Lunar Atmosphere and Dust
Environment Explorer' (LADEE) fired the spacecraft's engines on
Oct. 6, slowing it enough to be captured by lunar gravity.  LADEE is
now in orbit round the Moon.  Soon, the spacecraft will begin its
mission to study the Moon's exotic and diaphanous atmosphere, which is
very much affected by space weather.


PLANCK TELESCOPE SET FOR SWITCH-OFF
BBC News

The process of disposing of the Planck space telescope has begun.  The
satellite, which mapped the "oldest light" in the Universe in
unprecedented detail, has completed its mission and will be turned off
in a fortnight's time.  It is currently a million miles from the
Earth, and is undergoing some final engineering tests.  European Space
Agency controllers will initiate a big burn on Planck's thrusters,
pushing it away from the planet into a separate orbit.  A second burn
on 21 October will run the satellite's propellent supply to
exhaustion.  The batteries will be disconnected and the transmitters
switched off.  Final contact is scheduled for 23 October, and Planck
will just drift off.  Planck has returned a great deal of information,
recording thousands of objects in the sky not previously recognised.
But its main quest was to survey the Cosmic Microwave Background (CMB)
-- the "first light" to be emitted once a post-Big-Bang Universe had
cooled sufficiently to permit the formation of hydrogen atoms.  Before
that time, scientists say, the cosmos would have been so hot that
matter and radiation would have been 'coupled' - the Universe would
have been opaque.