New solar twin could shed light on another Earth (Forwarded)

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Thursday 23 March 2006

New solar twin could shed light on another Earth

ANU astronomers have discovered a nearby solar twin which may shed light
on the search for planets that are similar to Earth and that may even
support life.

HD98618 is only the second star found so far that is almost identical to
the Sun in age, size, temperature and chemistry, according to the
researchers Dr Jorge Meléndez, Ms Katie Dodds-Eden and Mr José Robles,
from the Research School of Astronomy and Astrophysics.

"This solar twin doesn't only have the same mass as the Sun, it was also
formed with the same 'chemical recipe'. So this star was equipped in the
same way as the Sun to form Earth-like planets," Mr Robles said.

"Hopefully, as new planet finding techniques are developed and refined,
astronomers will find whether HD98618 hosts terrestrial planets, which may
even contain life."

HD98618 lies a mere 126 light-years away in the northern constellation of
Ursa Major (the 'Big Dipper'). It is bright enough to see in binoculars,
but only in the Northern Hemisphere.

The researchers believe that HD98618 is about four billion years-old,
about 10 per cent younger than our own Sun. Its chemical properties are
almost identical to the Sun and to the other closest Sun twin, a star
known as 18 Scorpii, which was discovered a decade ago.

"It means that hypothetical terrestrial planets around this solar twin may
have had enough time to develop some kind of complex life, assuming the
time-scale for complex life formation is similar to Earth's," Dr Meléndez
said.

The team says that focused observations of the two stars by planet-hunter
teams could reveal or rule out within a few years giant planets, such as
our own Jupiter, around HD98618. "18 Scorpii and HD98618 offer hope to
find solar systems similar to our own in the Universe," Dr Meléndez said.

The discovery also has implications for research in other areas. Solar
twins are ideal for the absolute calibration of astronomical measuring
instruments. They can provide data useful in modelling the solar phenomena
that may affect climate change, and will help settle the argument about
the uniqueness or otherwise of our Sun and Solar System.

"We had a number of candidates with similar properties to the Sun, but
while we held out hope for each star that it would turn out to be really
special, it was not at all certain to happen. HD 98618 was one of the last
of our candidates to be analysed, so it was quite a surprise when we
discovered how it stood out from the other candidates, together with 18
Scorpii. It was very exciting -- I had to blink twice to be sure I wasn't
imagining it," Ms Dodds-Eden said.

The researchers made the discovery using the largest telescope in the
world, the 10m Keck I telescope on the summit of Hawaii's dormant Mauna
Kea volcano.

Their paper detailing the discovery will be published in Astrophysical
Journal Letters. Related images are available from the ANU Media Office.

IMAGE CAPTION:
[http://info.anu.edu.au/mac/Media/Med...D98618main.jpg
(34KB)]
Colour enhanced zoom around HD98618, created using information from the
Sloan Digital Sky Survey.