Kepler-22

Extrasolar Planets Encyclopaedia data

Kepler-22 is a Sun-like star in the northern constellation of Cygnus, the swan, that is orbited by a planet found to be unequivocally within the star's habitable zone. It is located at the celestial coordinates: Right Ascension 19:16:52.2, Declination +47°53′3.9″. With an apparent visual magnitude of 11.7, this star is too faint to be seen with the naked eye. It can be viewed with a telescope having an aperture of at least 4 in. The estimated distance to Kepler-22 is 644 ly.

Stellar characteristics
Kepler-22 is slightly smaller and cooler than the Sun, 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.

Planetary system
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. This was significant in that it was the first relatively small exoplanet (about ) confirmed to be orbiting within a star's habitable zone. 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.