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An ANU graduate student who believes the spectacular Omega Centauri
star cluster is not all it seems will challenge prevailing wisdom at
the General Assembly of the International Astronomical Union in Sydney
today.
Laura Stanford thinks that Omega Centauri may be the pitiful remnant
of a once enormous galaxy that has been ripped to pieces by the
gravity of our own galaxy, the Milky Way.
Her research, in collaboration with ANU colleagues Dr Gary Da Costa
and Professor John Norris, and Dr Russell Cannon from the
Anglo-Australian Observatory, conclusively shows that some stars in
Omega Centauri formed long after others.
A brilliant cluster of over one million stars in the southern
Australian sky and clearly visible to the naked human eye, the stars
of Omega Centauri have long been thought to have formed billions of
years ago, drifting peacefully together through space ever since.
"For a few years now there have been hints that there was something
very strange about Omega Centauri," Ms Stanford said. "Our new
observations show beyond reasonable doubt that Omega Centauri is not
what we all thought it was."
Once the first stars in a cluster are born, some of them explode,
which blasts away remaining interstellar gas, from which stars are
made. Even if some of this star forming gas survived the explosions,
Omega Centauri frequently passes through our own galaxy, the Milky
Way, which should strip any remaining gas.
"Once the gas is gone, no stars should form, but we're seeing lots of
these newer stars in Omega Centauri," Ms Stanford said.
According to Dr Da Costa, the team's research will now focus on how
the gas managed to stay inside the galaxy long enough to form the
younger stars.
"We are beginning to think Omega Centauri is not a normal star cluster
at all, but that perhaps it was once the centre of a whole galaxy, one
hundred times bigger than the cluster is now.
"This galaxy blundered too close to our own, the Milky Way, and was
torn apart by its gravity - all we see today are the few stars that
once lived in the middle of this galaxy. The rest have been wrenched
away and scattered all over the sky."
The team used a revolutionary new feature of the Anglo-Australian
Telescope to make their observations - the 2dF instrument, which
allows astronomers to measure the properties of hundreds of stars at
once.
Photographs available
ANU MEDIA OFFICE CONTACT: Amanda Morgan (02) 6125 5575/0416 249 245
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