- Australian scientists have helped narrow the search for
extraterrestrial life.
-
- Researchers from Melbourne's Swinburne University of
Technology have identified the part of our galaxy where Earth-like planets
capable of harbouring life are likely to flourish.
-
- It is called the Galactic Habitable Zone - an area where
rocky planets not only form easily, but can safely harbour life away from
deadly hazards such as exploding stars.
-
- The ring-shaped region contains about 10 per cent of
the galaxy's 200 billion or so stars and, aptly, includes our own sun.
-
- Scientists from Swinburne University of Technology and
the University of New South Wales wrote the research paper, which was published
in the journal Science.
-
- The three researchers used a model that examined whether
stars were likely to have life-bearing planets.
-
- Such stars need to be old, so their planets have time
to develop life.
-
- They need to contain metal, essential for the formation
of rocky planets.
-
- And they need to be away from supernovas, or exploding
stars, which can be fatal to life in neighbouring solar systems.
-
- Such stars, the team found, were concentrated in the
part of the galaxy they dubbed the Galactic Habitable Zone, between 23,000
and 30,000 light years away from the centre of the galaxy (which is about
100,000 light years wide).
-
- "Not surprisingly, Earth's solar system falls within
the zone, although it's younger and further from the galactic centre than
the average complex life-bearing planet," said a co-author of the
paper, Yeshe Fenner, from Swinburne's Centre for Astrophysics and Supercomputing.
-
- Stars that contain metals are most likely to harbour
rocky planets, although those with too much metal could be dangerous, the
researchers said.
-
- Stars that were too rich in metal spawned giant planets
with orbits dangerous to smaller, Earth-like planets.
-
- "There is a goldilocks zone of metallicity: with
too little metallicity, Earth-mass planets are unable to form, or with
too much metallicity, giant planets destroy Earth-mass planets," the
paper said.
-
- Another of the researchers, Professor Brad Gibson of
Swinburne, said the discovery of the GHZ did not mean advanced life necessarily
existed beyond Earth, "but if there is life, we've determined where
you are most likely to find it".
-
- "Our Milky Way galaxy is home to hundreds of billions
of stars but until recently astronomers could only guess as to how many
are hospitable for the development of complex life," said co-author
Dr Charles Lineweaver from the University of NSW. "What we have done
for the first time is to quantify carefully where complex (animal) life
is likely to exist."
-
- Copyright © 2004 The Age Company Ltd.
-
- http://www.theage.com.au/articles/2004/01/01/1072908849778.html?from=storyrhs
|
