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Scientists estimate Earth-sized planets could be common
Thursday, October 21, 2010 10:43:34 PM, DPA
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Washington:
A group of astronomers has estimated that as many as one in four
stars similar to the Sun could be orbited by Earth-size planets.
A five-year observation of 166 stars within 80 light years of
Earth, using the powerful Keck telescope in Hawaii, counted
planets orbiting the stars, down to the smallest planets now
detectable by telescopes.
In findings to be published in the journal Science Friday, the
researchers found larger numbers of smaller planets than of larger
planets. Although the smallest planets they saw are still several
times the size of Earth, the findings caused them to conclude that
Earth-sized planets could be even more common.
"Of about 100 typical Sun-like stars, one or two have planets the
size of Jupiter, roughly six have a planet the size of Neptune,
and about 12 have super-Earths between three and 10 Earth masses,"
astronomer Andrew Howard said.
"If we extrapolate down to Earth-size planets -- between one-half
and two times the mass of Earth -- we predict that you'd find
about 23 for every 100 stars."
The scientists found 33 detectable planets orbiting 22 of the
stars and then used estimates to conclude that 1.6 percent of the
stars had Jupiter-sized planets and 12 percent had super-Earths.
They also found 12 possible planets that need to be further
examined.
Previous studies have looked only at larger Jupiter and
Saturn-sized planets.
Astronomers hope to be able to find planets similar to Earth that
also are close enough to their suns to be warm and have liquid
water, but far enough away to not be boiling in the so-called
"Goldilocks" zone, where conditions are just right for life.
Last month, a group of US-based scientists said they had
discovered what might be the first habitable planet outside
Earth's solar system. The team of planet hunters found an
Earth-sized planet -- three times the mass of Earth -- in orbit
around a nearby star at a distance where liquid water could exist
on the surface.
Scientists hope the Kepler space telescope launched last year,
which is finely tuned enough to detect Earth-sized planets
orbiting distant stars, will find more such planets.
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