spacetoday.net: Kepler discovers planet in star's habitable zone

Posted: Tue, Dec 6, 2011, 7:43 AM ET (1243 GMT)
Kepler-22b illustration (NASA/Ames/JPL-Caltech)

Astronomers announced Monday the first discovery in data from NASA's Kepler mission of a planet in the habitable zone of a Sun-like star. The planet, designated Kepler-22b, is about 2.4 times the radius of the Earth and would have an average surface temperature of 22 degrees Celsius, but astronomers said they did not have information about the planet's mass or potential composition, thus making them unable to say just how much this planet may be like the Earth. The planet is the first world found by Kepler orbiting in the habitable zone of a star, where temperatures would permit the presence of liquid water. The spacecraft has now detected over 2,300 potential planets, including ten similar in size and orbit to the Earth, although followup observations are needed to confirm their existence. Scientists said the overall data collected by Kepler suggests that smaller planets, one to four times the size of the Earth, may be abundant.