[ASC-media] AUSSIES EXPLAIN DYING STAR'S MIXED MESSAGES
Darren.Osborne at csiro.au
Darren.Osborne at csiro.au
Thu May 4 15:53:32 EST 2006
Issued by Helen Sim, Anglo-Australian Observatory (Sydney, Australia)
hsim at aaoepp.aao.gov.au
Image links and full media release http://www.gemini.edu/2001igpr
4 May 2006
For immediate use
AUSSIES EXPLAIN DYING STAR'S MIXED MESSAGES
Australian astronomers have explained why a dying star sent out mixed
signals about its identity.
A cosmic explosion seen in 2001 looked like one particular kind of
dying star, but then mysteriously seemed to change into the
death-throes of another kind.
Dr Stuart Ryder of the Anglo-Australian Observatory and his colleagues
now say this odd behaviour was caused by a 'companion' star that still
lurks at the scene of the explosion.
Called supernova 2001ig, the explosion took place 37 million
light-years away in a galaxy called NGC 7424, and was first spotted in
2001 by a renowned Australian amateur supernova hunter, Bob Evans.
After studying the explosion, Ryder and his colleagues predicted the
existence of the companion star. They recently found it, using the
Gemini South telescope in Chile.
This is only the second time a companion has been found where a star
But Ryder thinks companion stars could explain much that has puzzled
"We've been putting supernovae into different categories for decades,
but it's been a mystery how some of the different types are related to
each other, and what's actually going on physically."
"In this case, the companion star and the one that exploded would have
been orbiting each other. We think the companion helped strip hydrogen
gas from the other star before it exploded," he said.
"There was a trace of hydrogen in the supernova early on, but it soon
disappeared. So at first it looked like we had one kind of star
exploding, but later on it looked quite different."
Two lines of evidence led the astronomers to suspect a companion was at
This supernova (called SN2001ig) was similar to another rare one found
in 1993 (called SN1993J). Astronomers found a companion at the site of
the 1993 supernova, suggesting that this supernova might have one too.
And observations made with a CSIRO radio telescope near Narrabri, NSW,
showed that there were thick patches of gas and dust in the space
around the star.
"That gas and dust was shed by the star before it died," explained
Ryder. "We think the orbiting companion swept it into a spiral shape -
the bumps and dips in our radio data fit such a spiral. And people have
seen these spirals around other stars with companions."
Dr Stuart Ryder, Anglo-Australian Observatory (Sydney)
sdr at aaoepp.aao.gov.au
A paper on the observations, "A post-mortem investigation of the Type
IIb supernova 2001ig", co-authored by Ryder, University of Tasmania
graduate student Clair Murrowood and former AAO astronomer Dr Raylee
Stathakis, was published online in Monthly Notices of the Royal
Astronomical Society on May 2. It is also available at
Galaxy NGC 7424 and the supernova field http://www.gemini.edu/2001igpr
Spirals of gas and dust around Wolf-Rayet stars, imaged by Dr Peter
Tuthill, University of Sydney
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the ASC-media