Kepler-22

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]

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
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]
Distance644 ± 1 ly
(197.5 ± 0.4 pc)
Absolute magnitude (MV)~5.27
Absolute bolometric
magnitude (Mbol)		~4.98
Details
Mass0.857+0.051
−0.043[5] M☉
Radius0.869±0.011[5] R☉
Luminosity (bolometric)0.79 ± 0.04[3] L☉
Luminosity (visual, LV)~0.67 L☉
Temperature5596±61[5] K
Metallicity [Fe/H]−0.255±0.065[5] dex
Rotational velocity (v sin i)0.6 ± 1.0[3] km/s
Age7.0+4.0
−4.2[5] Gyr
Other designations
Gaia DR2 2127941757262806656, KOI-87, KIC 10593626, GSC 03546-02301, 2MASS J19165219+4753040[6]
Database references
SIMBADdata
Exoplanet Archivedata
KICdata
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
The Kepler-22 planetary system[5]
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 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.[5]

References
  1. "Cygnus – constellation boundary", The Constellations, International Astronomical Union, retrieved 2011-12-15
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. "Kepler-22b". Archived from the original on 2017-03-31. Retrieved 2011-12-07.
  4. Schneider, Jean, "Star: Kepler-22", Extrasolar Planets Encyclopaedia, Paris Observatory, retrieved 2020-12-17
  5. Bonomo, A. S.; Dumusque, X.; et al. (April 2023). "Cold Jupiters and improved masses in 38 Kepler and K2 small-planet systems from 3661 high-precision HARPS-N radial velocities. No excess of cold Jupiters in small-planet systems". Astronomy & Astrophysics. arXiv:2304.05773. doi:10.1051/0004-6361/202346211. S2CID 258078829.
  6. "GSC 03546-02301 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-08
  7. Sherrod, P. Clay; Koed, Thomas L. (2003), A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations, Astronomy Series, Courier Dover Publications, p. 9, ISBN 0486428206
  8. "Kepler Confirms First Planet in Habitable Zone of Sun-Like Star". Universe Today. 2011-12-05.
  9. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
  10. Armstrong, D. J.; Pugh, C. E.; Broomhall, A.-M.; Brown, D. J. A.; Lund, M. N.; Osborn, H. P.; Pollacco, D. L. (2015), "The Host Stars of Kepler's Habitable Exoplanets: Superflares, Rotation and Activity", Monthly Notices of the Royal Astronomical Society, 455 (3): 3110–3125, arXiv:1511.05306, doi:10.1093/mnras/stv2419, S2CID 16265095
  11. Borucki, William J.; Koch, David G.; et al. (February 2012). "Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star". The Astrophysical Journal. 745 (2): 120. arXiv:1112.1640. Bibcode:2012ApJ...745..120B. doi:10.1088/0004-637X/745/2/120. S2CID 50813889.
  12. Boyle, Rebecca (December 5, 2011). "Kepler Team Confirms First Earth-like planet in a habitable zone, And Finds 1,094 More Worlds". Popular Science. Retrieved December 5, 2011.
  13. "NASA Telescope Confirms Alien Planet in Habitable Zone". Space.com. 2011-12-05.
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