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′ 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  19h 16m 52.1904s[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
Distance638 ± 3 ly
(195.7 ± 0.9 pc)
Absolute magnitude (MV)~5.27
Absolute bolometric
magnitude (Mbol)		~4.98
Details
Mass0.970 ± 0.060[3] M☉
Radius0.979 ± 0.020[3] R☉
Luminosity0.79 ± 0.04[3] L☉
Luminosity (bolometric)0.8 L☉
Luminosity (visual, LV)~0.67 L☉
Temperature5518 ± 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
SIMBADdata
KICdata

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⊕
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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.

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