Govert Schilling, ScienceNow
WIRED, 5 december 2011
For the first time, astronomers have found a planet smack in the middle of the habitable zone of its sunlike star, where temperatures are good for life. “If this planet has a surface, it would have a very nice temperature of some 70° Fahrenheit [21°C],” says William Borucki of NASA’s Ames Research Center here, who is the principal investigator of NASA’s Kepler space telescope. “[It’s] another milestone on the journey of discovering Earth’s twin,” adds Ames director Simon “Pete” Worden.
Unfortunately, the true nature of the planet, named Kepler-22b, remains unknown. It is 2.4 times the size of Earth, but its mass, and hence its composition, has not yet been determined. “There’s a good chance it could be rocky,” Borucki says, although he adds that the planet would probably contain huge amounts of compressed ice, too. It might even have a global ocean. “We have no planets like this in our own solar system.”
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Forty-eight of these planet candidates orbit in the habitable zone of their parent stars. Most are substantially larger than Earth, but 10 are about the same size as our home planet. Some of these are in multiplanet systems. “It’s conceivable that any — or many — of these 48 habitable zone candidates, or their moons, could have life,” Borucki says.