Topic: Late March Astronomy Bulletin

[Clive]

JUPITER'S RED SPOT
ESO

Astronomers have been observing Jupiter's Great Red Spot, an
elliptical storm about 25,000 miles across, for hundreds of years.
Now, they have been using the Very Large Telescope to take thermal
(far-nifrared) images of it.  They show that the most intense
orange-red central part of the spot is about 3 to 4 degrees warmer
than the -160C environment around it.  That temperature difference
might not seem much, but it is enough to allow the storm circulation,
usually counter-clockwise, to shift to a weak clockwise circulation
in the very middle of the storm.  Dark lanes at the edge of the storm
appear to mark places where gases are descending into the deeper
regions of the planet.  We still do not know what chemicals or
processes are causing the red colour, which now seems to be related to
changes in the environmental conditions right in the heart of the
storm.


NEW EXOPLANET 'MORE LIKE ONE OF OURS'
BBC News

A planet that has been named CoRoT-9b has been discovered by the CoRoT
satellite (a mission led by the French space agency, Centre National
d'Études Spatiales) around a star 1500 light-years away.  It is the
size of Jupiter and has an orbit similar to that of Mercury.  More
than 400 planets have been discovered outside the Solar System so far,
but this is the first one where it even makes sense to apply models
developed for planets within our Solar System -- the others are either
extremely hot, being very close to the central star, or they are on
eccentric orbits, taking them close to and far from the star so they
have extreme temperature ranges.  The surface temperature is estimated
(seemingly with no great accuracy) to be between about -20 and +160C.
During its orbit of 95 days it transits (passes in front of) its star
for about eight hours.  The fact that it transits ought to enable
astronomers to obtain much more information about it than they could
otherwise.


WHITE-DWARF STAR SYSTEM EXCEEDS MASS LIMIT
Yale University

Cosmologists use Type Ia supernovae -- violent explosions of the dead
cores of white-dwarf stars -- as a cosmic yardstick with which to
measure distances, in the hope ultimately of understanding the past
and future development of the Universe.  It has been thought that
white dwarfs could not exceed what is known as the Chandrasekhar
limit, a critical mass about 1.4 times that of the Sun, before
exploding in a supernova.  That uniform limit has been considered a
key tool in measuring distances to supernovae.  Since 2003, however,
four supernovae have been discovered that were so bright that
cosmologists felt impelled to wonder whether their white dwarfs had
surpassed the Chandrasekhar limit.  Now a collaboration of American
and French physicists claims to have determined the mass of the white
dwarf that resulted in one of the rare supernovae, called SN 2007if,
and confirmed that it exceeded the Chandrasekhar limit.  They also
discovered that the unusually bright supernova had not only a central
mass, but a shell of material that was ejected during the explosion,
as well as a surrounding envelope of pre-existing material.  The team
has made estimates of the masses of those three components separately.
The star itself appears to have had a mass of 2.1 times the mass of
the Sun (plus or minus 10%), putting it appreciably above the limit.

Scientists think that SN 2007if may have resulted from the merging of
two white dwarfs, rather than the explosion of a single white dwarf
that was not obeying the rules.  Naturally they hope to study the
other apparently super-Chandrasekhar supernovae to see whether they,
too, could have involved a merger of two white dwarfs, or whether it
is necessary to conclude that stars with masses above the limit could
somehow exist without collapsing under their own weight.


RAPID STAR FORMATION IN EARLY GALAXY
RAS

Scientists have found that in the early Universe a massive galaxy was
creating stars like our Sun up to 100 times faster than the modern-day
Milky Way.  Owing to the length of time it has taken its light to
reach the Earth, the galaxy, known as SMM J2135-0102, is seen now as
it would have appeared 10 billion years ago -- three billion years
after the Big Bang.  The galaxy is seen better than it would
ordinarily be, because it is magnified by the 'gravitational lens' of
other galaxies in the line of sight between it and us.  There were
four discrete star-forming regions within it, and each one was more
than 100 times brighter than star-forming regions like the Orion
Nebula in our own Galaxy.  The scientists estimate that the observed
galaxy was producing stars at a rate equivalent to 250 Suns per year.
This is not the first time that an early galaxy has been observed
producing stars at a rate far higher than seems to be the norm now.


SPITZER IDENTIFIES PRIMITIVE BLACK HOLES
JPL

Astronomers using the Spitzer space telescope have come across what
appear to be two of the earliest and most primitive quasars, born in a
dust-free medium and at the earliest stages of evolution.  Quasars are
small objects, that emit enormous amounts of energy, seen at the
centres of some glaxies, and are supposed to be powered by the infall
of material into super-massive black holes in their cores.

The present-day Universe is very dusty, but scientists believe that
there was no dust in the very early Universe -- so the most primitive
quasars should also be dust-free.  But nobody had seen such immaculate
quasars until now.  Spitzer has identified two -- the smallest on
record -- about 13 billion light-years away.  The quasars, called
J0005-0006 and J0303-0019, were first discovered in visible light in
the Sloan Digital Sky Survey.  The discovery team also observed X-rays
from one of the objects.  X-rays, ultraviolet and optical light stream
out from quasars as the gas surrounding them is swallowed by the black
hole.  The high luminosity of quasars makes them detectable literally
at the edge of the observable Universe.

Spitzer measured infrared light from the two objects along with 19
others, all belonging to a class of the most distant quasars known.
Each quasar is anchored by a super-massive black hole with a mass of
more than 100 million suns.  Of the 21 quasars, J0005-0006 and
J0303-0019 lacked characteristic signatures of hot dust.  Those early
black holes were forming around the time when the dust was first
forming in the Universe, less than one billion years after the Big
Bang.  The primordial Universe did not contain any molecules that
could coagulate to form dust; the elements necessary for dust were
produced later by stars.  The astronomers also observed that the
amount of hot dust in a quasar increases with the mass of its black
hole.  As a black hole grows, dust has more time to materialize around
it.  The black holes at the cores of J0005-0006 and J03031-0019 have
the smallest measured masses known in the early Universe, indicating
that they are particularly young, at a stage when dust has not yet
formed around them.