Topic: Late September Astronomy Bulletin

[Clive]

MISSION TO STUDY MOON FROM CRUST TO CORE
NASA

The twin lunar Gravity Recovery and Interior Laboratory (GRAIL)
spacecraft have been launched towards the Moon.  GRAIL-A is scheduled
to reach the Moon on New Year's Eve 2011, while GRAIL-B will arrive
on New Year's Day 2012. The two solar-powered spacecraft will fly in
tandem orbits around the Moon to measure its gravity field and (it is
hoped) may answer longstanding questions about the Moon.  The mean
distance to the Moon is just over 400,000 km, and it took the Apollo
astronauts approximately three days to cover that distance.  However,
the Grail spacecraft will be on a low-energy trajectory which will
take them more than 3 months and more than 4 million km, but the
phase of actual collection of scientific data is intended to last
only 82 days.


FIFTY NEW EXO-PLANETS FOUND
ESO

Astronomers using the HARPS spectrograph on the 3.6-m telescope at
La Silla in Chile have announced the discovery of more than 50 new
exo-planets, including 16 'super-Earths'.  One of them, HD 85512 b, is
estimated to be only 3.6 times the mass of the Earth.  Extrapolating
from the current census of planets, the team estimates that about 40%
of stars similar to the Sun may have at least one planet less massive
than Saturn.  In the eight years since it started surveying stars like
the Sun by the radial-velocity technique, HARPS has discovered more
than 150 planets, including about two-thirds of all known exo-planets
with masses less than that of Neptune.  The majority of those of
Neptune mass or less appear to be in systems with more than one
planet.  After recent improvements, HARPS is now so sensitive that it
can detect radial-velocity amplitudes of less than 4 km/hour -- hardly
walking speed, but still more than ten times the rate at which the Sun
is moved by the Earth.  New instruments are planned to further the
search for Earth-like planets.


HOW SINGLE STARS LOSE THEIR COMPANIONS
RAS

In our Galaxy, the Milky Way, about half of all stars have a companion
and travel through space in a binary system.  But it has not been
obvious why some stars are in double or even triple systems while
others are single.  Now astronomers from Bonn University and the
Max-Planck-Institute for Radio Astronomy (also in Bonn) think that
they have an answer -- different stellar birth environments decide
whether a star holds on to its companion.  Stars generally do not form
in isolation but are born together in groups within clouds of gas and
dust.  The Bonn scientists reckon that virtually all newborn stars
have a companion, but before the group disperses and its members become
mixed into the Galaxy, the binary pairs interact with others
gravitationally.  In many cases the pairs are torn apart into two
single stars.  The clouds within which new stars are born are of
differing sizes and densities.  The higher the density, the more
interaction is likely to take place between them and the more binary
systems will be liable to be split up into single stars.


KEPLER DISCOVERS A PLANET WITH TWO SUNS
NASA

The Kepler mission has made the first unambiguous detection of a
circum-binary planet -- a planet orbiting two stars -- 200 light-years
away.  The new planet, called Kepler 16b, is in the Kepler-16 system,
a pair of orbiting stars that eclipse each other.  Astronomers
observed that the brightness of the system sometimes dipped even when
the stars were not eclipsing one another, indicating the existence of
a third body.  The extra events occurred when the stars were in
different positions in their orbit, showing that the third body was
circling, not just one, but both stars, in a large circum-binary
orbit.  Kepler-16b is a cold planet about the size of Saturn and is
thought to be made up of about half rock and half gas; it orbits
the parent stars, which are smaller than our Sun, every 229 days.


HEAVY ELEMENTS FORMED IN NEUTRON-STAR COLLISIONS
Astropublishing

Astrophysicists at the Max Planck Institute for Astrophysics and the
Free University of Brussels have put forward the hypothesis that the
process that forms the majority of the heavy elements in the Universe
is collisions between neutron stars.  It appears that in the small
fraction of material that is ejected in such collisions (between 0.001
and 0.01 solar masses) the mix of heavy elements is similar to that
found in the Solar System and in stellar atmospheres.  The phase in
which the elements form is rather short-lived, and starts when the
temperature of the ejected plasma falls below 10 billion degrees.
Initially very heavy, very unstable nuclei are produced, which then
decay radioactively to form lighter elements.  The emission resulting
from the decay processes is so intense that the ejected material is as
luminous as a supernova.  When the environment cools, the nuclei
recombine with electrons in the plasma, creating more stable neutral
atoms which gradually pervade the surrounding space.


SKYNET SEEKS TO 'CROWD-SOURCE' THE STARS
BBC

Idle home computers are being sought to help search through mountains
of astronomical data.  The Skynet project involves using the spare
processing capacity of computers as a giant, distributed
super-computer.  PCs joining Skynet will scour the data for sources of
radiation that reveal stars, galaxies and other cosmic structures.
People who process the most data could win a visit to one of the
observatories gathering data for the project.  The Skynet project is
being run by the International Centre for Radio Astronomy Research
(ICRAR) and it is seeking the help of thousands of PCs.  One of the
sources of data will be the Square Kilometre Array (SKA) that will
consist of thousands of dish antennae; a choice between Australia and
South African sites for the array will be made in 2012.  The SKA will
of course have its own set of computers, but it is expected to produce
its data in such a dilute form that a system to filter them down to
the most interesting samples will be needed.  Skynet will be part of
that large-scale filtering system.

Skynet aims to complement the work already being done by creating a
'citizen science' computing resource that radio astronomers can tap
into and process data in ways and for purposes that otherwise might
not be possible.  Before the SKA is operating, the computers joining
ICRAR's Skynet will crunch data from current radio-astronomy research
projects.  Those signing up to help will download a small program that
will get a computer looking through data when that PC is not being
used for anything else.  ICRAR says that the Skynet program is small
and should not appreciably slow down any PC on which it is running.
Also, it says, data would be split into small packets to ensure they
did not swamp a participant's net connection.  Distributed computing
projects that harness idle machines are a well-established way of
scouring through research data.  One of the earliest looked through
radio signals for evidence of extra-terrestrial intelligence (but of
course it failed).