Stars well-endowed with gold have fewer companions (Forwarded)

MARKETING AND COMMUNICATIONS DIVISION
AUSTRALIAN NATIONAL UNIVERSITY
CANBERRA ACT 0200 AUSTRALIA

For interviews:

Dr Charley Lineweaver, 02 6125 6717
Dr Daniel Grether, 0418629543

ANU Media Office:
Simon Couper, 02 6125 4171, 0416 249 241

Thursday 8 Nov 2007

Stars well-endowed with gold have fewer companions

The chequered destinies of Australian Idol winners underscores what
astronomers have known for a long time -- star formation is complicated.

A new astronomical study adds an unexpected twist to the complications:
stars well-endowed with gold and other heavy elements have fewer stellar
companions. Researchers from The Australian National University (ANU) and
the University of New South Wales (UNSW) believe their discovery could
help track down Earth-like planets outside of our solar system.

"Ten years ago researchers found that stars with a large amount of heavy
elements were more likely to be orbited by planets," said report co-author
Dr Charley Lineweaver from ANU's Planetary Science Institute. "We still
don't understand why, but that's the way it is. Our goal was to find out
if such high-metallicity stars might also be more likely to be orbited by
other stars."

The Sun is a typical star in that about one per cent of its mass is made
of heavy elements like oxygen, iron and gold. However, there are many
stars with as little as one third of a per cent of their mass in heavy
elements, while other stars have tens times that much. The amount of heavy
elements somehow plays an important role in the types of object that form
around a star.

Dr Lineweaver and Dr Daniel Grether from UNSW put together the most
complete census of nearby stars, including the amount of heavy elements in
these stars and whether the stars had planetary or stellar companions.
They were surprised when they found the opposite of what was expected --
stars with the highest content of heavy elements were less likely, not
more likely, to have stellar companions.

"Our counterintuitive result does not yet have a good theoretical
explanation, but we think that stars that form in different regions of our
galaxy probably followed different paths to stardom," Dr Grether said.

Detecting Earth-like planets has become a hot field for astronomers. Dr
Lineweaver and Dr Grether believe that further research on the
relationship between the amount of heavy elements in stars and the types
of stellar and planetary companions orbiting them could assist in the
search for worlds like our own.

The study is published in the latest edition of the Astrophysical Journal:
http://www.journals.uchicago.edu/ApJ...pJ/v669n2.html

A local link to a pdf of the published version of the paper can now be
found at
http://www.mso.anu.edu.au/~charley/publications.html