Gas 'finger' points to Magellanic Clouds' future (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 13 Feb 2008 01:19:36 GMT
Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Clayton, Australia
Primary Contact:
Dr Naomi McClure-Griffiths (BA PhD)
CEO Science Leader
Australia Telescope National Facility
Phone: 61 2 9372 4321
Fax: 61 2 9372 4310
Media Contact:
Ms Helen Sim (BSc MSc Soc GradDipPubRel)
Media and Public Relations
Australia Telescope National Facility
Phone: 61 2 9372 4251
Fax: 61 2 9372 4444
5 February 2008
Reference: 08/16
Gas 'finger' points to galaxies' future
Like a fork piercing a fried egg, a giant finger of hydrogen gas is poking
through our Milky Way Galaxy from outside, astronomers using CSIRO radio
telescopes at Parkes and Narrabri have found.
The location of the intrusion may give a crucial clue to the fate of the
little galaxies the gas flows from, the Large and Small Magellanic Clouds.
"We're thrilled because we can determine exactly where this gas is
ploughing into the Milky Way -- it's usually extremely hard to get
distances to such gas features," said the research team leader, Dr Naomi
McClure-Griffiths of CSIRO's Australia Telescope National Facility.
The gas finger, called HVC306-2+230, is running into the starry disk of
our Galaxy about 70 thousand light-years (21kpc) away from us. On the sky,
the point of contact is near the Southern Cross.
The finger is the pointy end of the so-called Leading Arm of gas that
streams ahead of the Magellanic Clouds towards the Milky Way.
Until last year, astronomers generally thought that the Magellanic Clouds
had orbited our Galaxy many times, and were doomed to be ripped apart and
swallowed by their gravitational overlord.
But then new Hubble Space Telescope measurements showed the Clouds were
moving much faster than previously thought. In turn, this implied that the
Clouds are paying our Galaxy a one-time visit rather than being its
long-term companions.
Knowing where the Leading Arm is crossing the Galactic Disk may help
astronomers to predict where the Clouds themselves will go in future.
"We think the Leading Arm is a tidal feature, gas pulled out of the
Magellanic Clouds by the Milky Way's gravity," said Dr McClure-Griffiths.
"Where this gas goes, we'd expect the Clouds to follow, at least
approximately."
The team's measurement of where the Leading Arm intrudes into the Milky
Way is more in line with the models that assume the Magellanic Clouds have
been orbiting our Galaxy than with the models that have the Clouds just
passing by.
Dr McClure-Griffiths cautions that this is not the final word on the
subject, saying that the latter models were far from ruled out.
But the new result suggests that the Magellanic Clouds will eventually
merge with the Milky Way, rather than zooming past.
Publication
N. M. McClure-Griffiths et al. "An Interaction of a Magellanic Leading Arm
High Velocity Cloud with the Milky Way Disk." Astrophysical Journal
Letters; Vol 673 No L143; 1 February 2008.
[NOTE: Images supporting this release are available at
http://www.scienceimage.csiro.au/mediarelease/mr08-16.html ]
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