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Kepler-22 is slightly smaller and cooler than the Sun,[1] with a lower abundance of elements having more mass than helium. It has a spectral type of G5V, while the luminosity class remains undetermined. This star is radiating 79% of the Sun's luminosity from its outer atmosphere at an effective temperature of 5,518 K, giving it the yellow-hued glow of a G-type star. A projected rotational velocity of 0.6 km/s suggests it has a long period of rotation. No flare activity has been detected.
On December 5, 2011, scientists from the Kepler mission announced that an exoplanet, Kepler-22b, had been discovered orbiting in the star's habitable zone by NASA's Kepler spacecraft.[2] This was significant in that it was the first relatively small exoplanet (about) confirmed to be orbiting within a star's habitable zone.[3] Its size suggests that it is not a rocky planet and is more likely to be a mini-Neptune or ocean world; while its mass has not been measured, radial velocity observations have set an upper limit of .