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Spectral type G / M[1]
Distance ~1957 ly
(~600 pc)
Primary Kepler-38A
Companion Kepler-38B
Period (P) 18.79537
Semi-major axis (a) 0.1469
Eccentricity (e) 0.1032
Mass 0.949 M
Radius 1.757 R
Temperature 5640 K
Metallicity -0.11
Mass 0.249 M
Radius 0.2724 R
Metallicity -0.11
Other designations

Kepler-38 is a binary star system. These stars, called Kepler-38A and Kepler-38B have masses of 95% and 25% solar masses respectively. The brighter star is spectral class G while the secondary has spectral class M. They are separated by 0.147 AU, and complete an eccentric orbit around a common center of mass every 18.8 days.[2]

Planetary system[edit]

In 2012, a circumbinary Neptune-sized planet was found transiting the brighter star. Follow-up radial velocity measurements did not give sufficient information to constrain the mass of the planet. The planet was confirmed via transit duration variation method.

The Kepler-38 planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 0.4644 105.595 0.39 RJ

See also[edit]


  1. ^ "Notes for star Kepler-38(AB)". Extrasolar Planets Encyclopaedia. 2012. Retrieved 29 April 2013. 
  2. ^ The Neptune-Sized Circumbinary Planet Kepler-38b, 18 August 2012 Jerome A. Orosz, William F. Welsh, Joshua A. Carter, Erik Brugamyer, Lars A. Buchhave, William D. Cochran, Michael Endl, Eric B. Ford, Phillip MacQueen, Donald R. Short, Guillermo Torres, Gur Windmiller, Eric Agol, Thomas Barclay, Douglas A. Caldwell, Bruce D. Clarke, Laurance R. Doyle, Daniel C. Fabrycky, John C. Geary, Nader Haghighipour, Matthew J. Holman, Khadeejah A. Ibrahim, Jon M. Jenkins, Karen Kinemuchi, Jie Li, Jack J. Lissauer, Andrej Prsa, Darin Ragozzine, Avi Shporer, Martin Still, Richard A. Wade