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  19^h 16^m 52.2^s, Declination +47° 53′ 4.2″.[6] 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 638 light-years (196 parsecs).[2]

Kepler-22

A diagram of the Kepler-22b System, compared to our Inner Solar System.
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus[1]
Right ascension	19^h 16^m 52.1904^s[2]
Declination	+47° 53′ 03.948″[2]
Apparent magnitude (V)	11.664[3]
Characteristics
Spectral type	G5V[4]
Astrometry
Proper motion (μ)	RA: −39.717±0.052[2] mas/yr Dec.: −66.687±0.046[2] mas/yr
Parallax (π)	5.1088 ± 0.0242[2] mas
Distance	638 ± 3 ly (195.7 ± 0.9 pc)
Absolute magnitude (MV)	~5.27
Absolute bolometric magnitude (Mbol)	~4.98
Details
Mass	0.970 ± 0.060[3] M☉
Radius	0.979 ± 0.020[3] R☉
Luminosity	0.79 ± 0.04[3] L☉
Luminosity (bolometric)	0.8 L☉
Luminosity (visual, LV)	~0.67 L☉
Temperature	5518 ± 44[3] K
Metallicity [Fe/H]	–0.29 ± 0.06[3] dex
Rotational velocity (v sin i)	0.6 ± 1.0[3] km/s
Other designations
KOI-87, KIC 10593626, GSC 03546-02301, 2MASS J19165219+4753040[5]
Database references
SIMBAD	data
KIC	data

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 low period of rotation.

Planetary system

On December 5, 2011, scientists from the Kepler mission announced that a possible Earthlike world (Kepler-22b) had been discovered orbiting in the star's habitable zone by NASA's Kepler spacecraft.[10] This was significant in that it was the first relatively Earth-sized extrasolar planet (about twice as big)[10] confirmed to be orbiting within a star's habitable zone.[11]

The Kepler-22 planetary system[4]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	< 0.11 MJ	0.849 ± 0.018	289.8623 ^+0.016 −0.02	—	—	2.4 R⊕

References

1. "Cygnus – constellation boundary", The Constellations, International Astronomical Union, retrieved 2011-12-15
2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
3. Kepler-22b, NASA Ames Research Center, retrieved 2011-12-06
4. Schneider, Jean, "Star: Kepler-22", Extrasolar Planets Encyclopaedia, Paris Observatory, retrieved 2011-12-06
5. "GSC 03546-02301 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2011-12-08
6. "Kepler Discoveries". 2011-12-05.
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 10, 2012, retrieved 2012-01-16
10. 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.
11. "NASA Telescope Confirms Alien Planet in Habitable Zone". Space.com. 2011-12-05.