Kepler-22b is the first confirmed extrasolar planet found by NASA's Kepler Space Telescope to orbit within the habitable zone of a Sun-like star. Kepler-22b, a possible super-Earth, is 600 light years away from Earth, in orbit around Kepler-22, a G-type star.The discovery was announced December 5, 2011. The planet was originally discovered on Kepler's third day of science operations in mid-2009.The third transit was detected in late 2010. Additional confirmation data was provided by the Spitzer Space Telescope and ground-based observations.Kepler-22b's radius is roughly 2.4 times the radius of Earth, or about 60% that of Neptune. Its mass and surface composition remain unknown, with only some very rough estimates established: It has less than 124 Earth masses at the 3 sigma confidence limit, and less than 36 Earth masses at 1 sigma confidence.
It has been estimated that it is probably a "Neptunian" (i.e. mass similar to Neptune) planet with a mass of ~35 Earth masses. There are the possibilities that it could be an "ocean-like" world with only some 10 Earth masses. It might also be comparable to GJ 1214 b in terms of radius, but Kepler-22b is, unlike that planet, in the habitable zone. If it has an Earth-like density (5.515 g/cm3) then it would contain 13.8 Earth masses,[note 1] while its surface gravity would be 2.4 times Earth's.[note 2]
Since Kepler-22b is substantially larger than our planet, it is likely to have a different composition than Earth, and depending on its actual mass, the planet could be rocky, liquid, or gaseous..
If it is mostly ocean with a small rocky core, Natalie Batalha, one of the scientists on the project, speculated "it's not beyond the realm of possibility that life could exist in such an ocean." This possibility of life has spurred SETI to perform research on top candidates for extraterrestrial intelligence. However, if the planet's carbon cycle has ceased due to lack of oceans and...
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