- Astronomers may have had their first
glimpse of Earth-like planets beyond the Solar System. The results are
still very tentative, but even if the planets turn out to be a false alarm,
the researchers say they have shown that an unexpectedly powerful technique
for planet-hunting can work.
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- Around a dozen extrasolar planets have
been discovered over the past three years. All have masses comparable to
Jupiter, suggesting they are gassy giants that could never host life. Small
rocky planets the size of Earth or Mars would be more likely to have the
right conditions for life. But until now, astronomers thought that they
lacked the techniques to detect such small extrasolar planets.
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- Now an international team has proved
this wrong. Since 1994 the researchers have monitored a binary star system
called CM Draconis, roughly 60 light years away, using 10 telescopes around
the globe. They were looking for a slight dimming of the system during
"transits", as planets pass in front.
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- The researchers say they saw several
dips that could not be explained by factors such as calibration errors
or dust in the Earth's atmosphere. "There are some tantalising events,"
says team member Jon Jenkins of NASA's Ames Research Center in California.
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- If the light dips are caused by one or
more planets passing in front, their diameters would lie in the range of
roughly 1·5 to 3 times that of the Earth--the range the experiment
is designed to detect. The results will appear in Astronomy and Astrophysics.
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- The team has still to analyse the data
gathered over the past year, which should allow the researchers to confirm
or deny the existence of the planets. In the meantime, the cause for celebration
is that their technique can work.
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- "Their technique is sound,"
agrees Geoff Marcy of the University of California at Berkeley, who has
helped find most of the giant extrasolar planets. He adds that confirmation
of any planets will only come if the team can see periodic orbits and predict
when a light dip is due. "The proof of the pudding is a prediction
about when the transits should occur."
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