An artist's rendering shows the two Saturn-sized planets discovered by NASA's Kepler mission, which also found a planet sized similarly to Earth.
Scientists working with NASA's Kepler satellite reported Thursday that they might have spotted a planet just 1.5 times the diameter of Earth around a Sun-like star 2,000 light-years away.
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"We're still in the process of confirming this candidate is a planet," said Matthew Holman, of the Harvard-Smithsonian Center for Astrophysics, at a NASA-sponsored news conference on Thursday. Dr. Holman is the lead author of an article describing the discoveries that the journal Science published on its Web site.
This is the first announcement of a candidate Earth-size planet by the Kepler mission, which in March 2009 launched a one-ton spacecraft to search for planets like ours that just might harbor life. The planet was among more than 700 candidate planets that the team announced in June. If it is made of similar stuff as Earth, its mass would be three to four times as much.
Astronomers are quickly closing in on Earth-size planets elsewhere in the galaxy as they find planetary systems that look more and more like our solar system.
"This represents a significant step toward Kepler's goal of determining the frequency of Earth-size planets in the habitable zones of Sun-like stars," Dr. Holman said. Earth-size planets in orbits that are not too hot or too cold are considered the most likely places to look for life elsewhere in the universe.
The Kepler team also observed, more definitively, two giant, Saturn-size gas planets around the same star, known as Kepler-9.
On Tuesday, a European team reported what may be a smaller planet, with
mass as little as 1.4 times that of Earth, around a star 127 light-years
away.
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Source: Kenneth Chang, The New York Times
