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Star Formation may spread 'Like a Bushfire'

Star formation may jump from place to place inside a galaxy like a
bushfire front, according to a team of astronomers from the UK,
Australia and Spain. The team used the Hubble Space Telescope and other
telescopes to study a galaxy called NGC 2903, which lies 25 million
light-years away and is similar to our own galaxy.

The HST picture shows that known 'hot spots' near the centre of the
galaxy are clusters of stars born 5 to 10 million years ago. Other
spots in the galaxy are clouds of ionised hydrogen gas where young
stars are forming today.

The two kinds of spots are far apart, meaning that star-forming
activity is shifting from place to place.

"It's moving surprisingly fast, about a million kilometres a year on
average," says team member Dr Stuart Ryder of the Anglo-Australian
Observatory in Sydney.

Stars form when a giant cloud of cold hydrogen gas collapses in on

"Star formation may be like a bushfire," says Dr Ryder. "Once it has
burnt out an area, it has to move on to where there's more fuel, or it
will die out."

"Perhaps when one cloud of gas is used up by being turned into stars,
the star-forming process starts in a neighbouring cloud, possibly
triggered by shock waves from stars exploding nearby."

The astronomers also found that a dense region of stars in the galaxy,
called a bar, seems to funnel gas into the galaxy's centre, fuelling
the birth of young stars.

"The centre of this galaxy is like a retirement village," Dr Ryder
says. "Most of the stars are old. But we see a bit more action in
places - a couple of discos starting up. That means there are some
younger inhabitants as well."

The research team members are Almudena Alonso-Herrero (University of
Hertfordshire, UK), Stuart D. Ryder (Anglo-Australian Observatory,
Sydney, Australia) and Johan H. Knapen (Isaac Newton Group of
Telescopes, Spain and the University of Hertfordshire, UK).

The research results are described in Alonso-Herrero et al. (2001)
available at The paper will
be published in a forthcoming issue of Monthly Notices of the Royal
Astronomical Society.

The Hubble Space Telescope is a project of international co-operation
between the European Space Agency and NASA.

Image credit: ESA & NASA


Dr Stuart Ryder, Anglo-Australian Observatory, Sydney, Australia

Dr Almudena Alonso-Herrero, University of Hertfordshire, United
(presently travelling in India)

Dr Johan H. Knapen, Isaac Newton Group of Telescopes, Spain

Helen Sim
Public Relations officer
Anglo-Australian Observatory
PO Box 296
Epping NSW 2121
tel: +61 2 9372 4251
fax: +61 2 9372 4444

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