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Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 57m 37.682s[1]
Declination +44° 2′ 6.17″[1]
Apparent magnitude (V) 13.9
Mass 1.347 M
Radius 1.793 R
Luminosity 0.669 L
Temperature 6297 K
Other designations
KIC 8191672, KOI-18
Database references
KIC data

Kepler-5 is a star located in the constellation Cygnus in the field of view of the Kepler Mission, a NASA project aimed at detecting planets in transit of, or passing in front of, their host stars as seen from Earth. One closely orbiting, Jupiter-like planet, named Kepler-5b, has been detected around Kepler-5. Kepler-5's planet was one of the first five planets to be discovered by the Kepler spacecraft; its discovery was announced on January 4, 2010 at the 215th meeting of the American Astronomical Society after being verified by a variety of observatories. Kepler-5 is larger and more massive than the Sun, but has a similar metallicity, a major factor in planet formation.

Nomenclature and history[edit]

Kepler-5 is named so because it was the fifth planet-bearing star discovered during the course of the Kepler Mission, a NASA operation that seeks to discover Earth-like planets that transit, or cross in front of, their host stars with respect to Earth.[2] The star's planet, Kepler-5b, was the second of the first five planets to be discovered by the Kepler spacecraft; the first three planets found by Kepler were used as tests, and had already been discovered.[3] Kepler-5b was presented to the public on January 4, 2010 at the 215th meeting of the American Astronomical Society in Washington, D.C., along with planets around Kepler-4, Kepler-6, Kepler-7, and Kepler-8.[4]

Kepler-5b's initial discovery by Kepler was re-examined by scientists at the W.M. Keck Observatory at Mauna Kea, Hawaii; the McDonald Observatory in west Texas; the Palomar and Lick Observatories in California; the MMT, WIYN, and Whipple Observatories in Arizona; and the Roque de los Muchachos Observatory in the Canary Islands.[5]


Kepler-5 is a sunlike star that is 1.374 (± 0.056) Msun and 1.793 (± 0.053) Rsun, and is 137% the mass of and 179% the radius of the Sun. The star has a metallicity of [Fe/H] 0.04 (± 0.06), making it approximately as metal-rich as the Sun,[6] therefore increasing the star's likelihood to have planets in orbit.[7] Kepler-5 has an effective temperature of 6297 (± 60) K, which is hotter than the Sun's effective temperature of 5778 K.[8] Kepler-5 has an apparent magnitude of 13.4, and cannot be seen with the naked eye.[3]

Planetary system[edit]

A picture showing the relative sizes of the first five planets discovered by Kepler. Kepler-5b is the second largest, highlighted in blue.

Kepler-5b is 2.114 MJ and 1.431 RJ. It is, thus, more than twice the mass of Jupiter, and slightly less than three halves of Jupiter's radius. Kepler-5b orbits its star every 3.5485 days, lying at approximately .05064 AU from Kepler-5. It is, thus, a Hot Jupiter, or a gas giant that orbits near to its host star.[3] To compare, Mercury orbits the sun at .3871 AU every 87.97 days.[9] The planet's eccentricity is assumed to be 0, which is the eccentricity for a circular orbit.[3]

The Kepler-5 planetary system[3]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 2.114 MJ 0.05064 3.5485 0 1.431 RJ

See also[edit]


  1. ^ a b Cutri, R. M. (2003). "2MASS All-Sky Catalog of Point Sources". VizieR On-line Data Catalog. Bibcode:2003yCat.2246....0C. 
  2. ^ "Kepler: About the Mission". Kepler Mission. NASA. 2011. Retrieved 26 February 2011. 
  3. ^ a b c d e "Summary Table of Kepler Discoveries". NASA. 2010-08-27. Retrieved 2010-10-16. 
  4. ^ Rich Talcott (5 January 2010). "215th AAS meeting update: Kepler discoveries the talk of the town". Astronomy magazine. Retrieved 26 February 2011. 
  5. ^ "NASA's Kepler Space Telescope Discovers its FIrst Five Exoplanets". NASA. 4 January 2010. Retrieved 26 February 2011. 
  6. ^ "Notes for star Kepler-5". Extrasolar Planets Encyclopaedia. 2010. Archived from the original on 21 January 2011. Retrieved 26 February 2011. 
  7. ^ Henry Bortman (12 October 2004). "Extrasolar Planets: A Matter of Metallicity". Space Daily. Retrieved 26 February 2011. 
  8. ^ David Williams (1 September 2004). "Sun Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 26 February 2011. 
  9. ^ David Williams (17 November 2010). "Mercury Fact Sheet". Goddard Space Flight Center. NASA. Retrieved 26 February 2011. 

Coordinates: Sky map 19h 57m 37.7s, +44° 2′ 6.2″