METEORITE CONTAINS MANY MOLECULES
BBC News
Scientists have been re-examining the Murchison meteorite, which fell
in a town of that name in Australia in 1969. It has been examined
before by scientists looking for specific compounds, but this is the
first non-targeted analysis. It has been found to contain a huge
variety of carbon-based chemicals. The team identified 14,000
different compounds, including 70 amino acids, in a sample of the
meteorite. The researchers say that the meteorite could have
originated before the Sun was formed, 4.5 billion years ago, and
probably passed through clouds of material in the early Solar System,
picking up the chemicals.
YOUNGEST EXTRA-SOLAR PLANET ORBITING SOLAR-TYPE STAR
Journal of Astronomy & Astrophysics
Astronomers have discovered the youngest extra-solar planet, around a
solar-type star named BD +20 1790. The giant planet, six times the
mass of Jupiter, is said to be only 35 million years old. It orbits a
young active star at a distance closer than Mercury orbits the Sun.
Young stars are usually excluded from planet searches because they
have intense magnetic fields that generate a range of phenomena known
collectively as stellar activity, including flares and spots. Such
activity can mimic the presence of a companion and so can make it
difficult to disentangle the signals of planets and activity.
The planet was detected by searching for very small variations in the
radial velocity of the host star, caused by the gravitational effect
of the planet as it orbits. Overcoming the interference caused by the
star's activity was a challenge for the team, but with enough data
from large telescopes, including ones at Calar Alto and La Palma, the
planet's signature was revealed. At present we know almost nothing
about the early stages of planet evolution. Most planet-search
surveys tend to investigate much older stars, with ages in excess of a
billion years. Only one young planet was previously known, and that
has an age of something like 100 million years.
FEWER STARS BORN TODAY THAN IN EARLY UNIVERSE
University of Arizona
Astronomers have known for some time that in the early Universe
galaxies formed new stars at a much faster rate than they do now.
It has not been known whether that was because they somehow formed
stars more efficiently, or because more raw material -- molecular gas
and dust -- was available. Compared to the average galaxy today,
which produces stars at rates equivalent to about ten solar masses per
year, the rate of star formation in the same galaxies appears to have
been up to ten times higher when they were younger. In efforts to
find an answer, observers have tended to look at some of the brightest
objects, mostly because the instruments available did not allow the
study of less extreme, more typical galaxies. Now, researchers have
used radio maethods and more sensitive instruments on the Hubble and
Spitzer space telescopes to observe a dozen distant 'normal' galaxies
to get a more complete picture of how galaxies make stars. They have
found that typical galaxies in the early Universe contained three to
ten times more molecular gas than today, a strong indication that the
rate of star formation has slowed down simply because there is less
raw material available now, and not because there has been any change
in the efficiency with which they make new stars.
MAGNETISM INFLUENCES MASSIVE STARS' FORMATION
RAS
A team of astronomers at Bonn University has used the MERLIN radio
telescope network centred at Jodrell Bank to show that magnetic fields
play an important role during the birth of massive stars. Magnetic
fields are already known to influence the formation of lower-mass
stars like the Sun. The new study indicates that the ways in which
high-mass and low-mass stars form may be more similar than previously
suspected. Stars more than 8 times the mass of the Sun, though rare,
dominate the content and evolution of the interstellar material in the
Galaxy and are responsible for the production of heavy elements such
as iron. However, the question of how massive stars are formed has
been hard to answer. The role of magnetic fields in particular has
been a topic of debate; many scientists thought that radiation and
turbulence would be the dominant factors, and hence the formation
process would be significantly different from that of less massive
stars such as our Sun. While magnetic fields have been observed in
the clouds of molecular hydrogen from which stars form, observations
close to massive stars have up to now been in short supply. Now,
astronomers have managed to observe the 3-dimensional magnetic-field
structure around the massive newly forming star (or proto-star)
Cepheus A HW2. They saw that its structure is surprisingly similar to
the way the field looks when much smaller stars form. At a distance
of 2300 light-years, Cepheus A is one of the nearest regions where
massive stars are forming, and earlier observations of that region
revealed a disc from which the gas falls on to HW2. In the new
observations, the astronomers have found that the magnetic field is
surprisingly regular and strong, implying that it is controlling how
the matter is transferred through the disc to feed the growing star.
To determine the magnetic field structure, the researchers used the
newly upgraded MERLIN telescope array to observe radio waves (with a
wavelength of approximately 5 cm) that are amplified by methanol
molecules. The methanol molecules, the simplest of the alcohol
compounds, are found in regions which surround the massive disc around
HW2 and extend over a domain 10 times the size of our Solar System.
Such regions are called masers, because they amplify microwave
radiation in the same way a laser amplifies light radiation. Even
though a strong magnetic field produces only a very weak signature in
the signal from the methanol molecules, the amplification is strong
enough to make the new observations possible.
ALIEN STAR CLUSTERS IN THE MILKY WAY
RAS
Around a quarter of the star clusters in our Milky Way galaxy
originated in other galaxies, according to a team of scientists from
Swinburne University of Technology in Australia. Previously
astronomers had suspected that some globular star clusters, which each
contain between 10000 and several million stars, were foreign to our
galaxy, but it was difficult positively to identify which ones. The
scientists think that their new review of the properties of globular
clusters in our galaxy has identified characteristics that point to an
external origin for about a quarter of them. The work also suggests
that the Milky Way may have swallowed up more dwarf galaxies than was
previously thought. Many of the foreign clusters originally existed
within dwarf galaxies. Although the dwarf galaxies get broken up by
the gravitational tide of the Milky Way and their individual stars are
dispersed, their globular star clusters remain intact and survive the
accretion process.
NEW PHOBOS FLY-BY SEASON
ESA
Mars Express has just began a series of fly-bys of Phobos, the larger
moon of Mars. The campaign will reach its climax on March 3, when the
spacecraft will make its closest pass to Phobos, skimming by at just
50 km. Because Mars Express is in an elliptical and polar orbit with
a maximum distance from Mars of about 10,000 km, it regularly passes
Phobos. The latest Phobos fly-by series began on February 16 when
Mars Express drew to within 991 km of Phobos' surface. The fly-bys
will continue at varying altitudes until March 26 when Phobos moves
out of range.
Last year the orbit of Mars Express was adjusted to prevent the
closest approach of the spacecraft drifting onto the planet's night
side, and the opportunity was taken to make its orbit pass close to
Phobos. The 50-km pass pass will enable Phobos' gravity field to be
mapped to some extent. At that range, Mars Express should feel
differences in the gravity of Phobos depending ypon which part of the
moon is closest at the time. That will allow scientists to infer the
moon's internal structure. Previous Mars Express fly-bys have already
provided an accurate mass for Phobos, and its stereo camera has
allowed an estimate to be made of the volume. The resulting density
has suggested that parts of Phobos may be hollow.
Topic: Late February Astronomy Bulletin (Read 620 times)