Kepler-22
Star in the constellation Cygnus
From Wikipedia, the free encyclopedia
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 19h 16m 52.2s, Declination +47° 53′ 3.9″.[2] With an apparent visual magnitude of 11.7,[3] 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 (10 cm).[7] The estimated distance to Kepler-22 is 644 light-years (197 parsecs).[2]
This diagram compares the Solar System to Kepler-22 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[1] |
| Right ascension | 19h 16m 52.19023s[2] |
| Declination | +47° 53′ 03.9486″[2] |
| Apparent magnitude (V) | 11.664[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2] |
| Spectral type | G5V[4] |
| Astrometry | |
| Radial velocity (Rv) | −4.50±0.51[2] km/s |
| Proper motion (μ) | RA: −39.589 mas/yr[2] Dec.: −66.773 mas/yr[2] |
| Parallax (π) | 5.0627±0.0110 mas[2] |
| Distance | 644 ± 1 ly (197.5 ± 0.4 pc) |
| Absolute magnitude (MV) | ~5.27 |
| Absolute bolometric magnitude (Mbol) | ~4.98 |
| Details | |
| Mass | 0.857+0.051 −0.043[5] M☉ |
| Radius | 0.869±0.011[5] R☉ |
| Luminosity (bolometric) | 0.79 ± 0.04[3] L☉ |
| Luminosity (visual, LV) | ~0.67 L☉ |
| Temperature | 5596±61[5] K |
| Metallicity [Fe/H] | −0.255±0.065[5] dex |
| Rotational velocity (v sin i) | 0.6 ± 1.0[3] km/s |
| Age | 7.0+4.0 −4.2[5] Gyr |
| Other designations | |
| KOI-87, KIC 10593626, GSC 03546-02301, 2MASS J19165219+4753040, Gaia DR2 2127941757262806656[6] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| KIC | data |
| Extrasolar Planets Encyclopaedia | data |
Stellar characteristics
Kepler-22 is slightly smaller and cooler than the Sun,[8] with a lower abundance of elements having more mass than helium.[3] It has a spectral type of G5V, while the luminosity class remains undetermined.[4] This star is radiating 79%[3] of the Sun's luminosity from its outer atmosphere at an effective temperature of 5,518 K,[3] giving it the yellow-hued glow of a G-type star.[9] A projected rotational velocity of 0.6 km/s[3] suggests it has a long period of rotation. No flare activity has been detected.[10]
Planetary system
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | <9.1 M🜨 | 0.812+0.011 −0.013 |
289.863876±0.000013 | <0.72 | 89.764+0.025 −0.042° |
2.10±0.12 R🜨 |
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.[11][12] This was significant in that it was the first relatively small exoplanet (about 2.4 R🜨)[12] confirmed to be orbiting within a star's habitable zone.[13] Its size suggests that it is not likely to be 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 9.1 M🜨 as of 2023[update].[5]