Kepler-38

Kepler-38 is a binary star system in the constellation Lyra. 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.^[3]

Kepler-38

Observation data Epoch J2000      Equinox J2000
Constellation	Lyra[1]
Right ascension	19h 07m 19.2813s[2]
Declination	+42° 16′ 45.121″[2]
Characteristics
Spectral type	G V[3] / M[4]
Astrometry
Proper motion (μ)	RA: −4.575(14) mas/yr[2] Dec.: −13.219(14) mas/yr[2]
Parallax (π)	0.8546±0.0119 mas[2]
Distance	3,820 ± 50 ly (1,170 ± 20 pc)
Orbit
Primary	Kepler-38A
Companion	Kepler-38B
Period (P)	18.79537
Semi-major axis (a)	0.1469
Eccentricity (e)	0.1032
Details
Kepler-38A
Mass	0.949 M☉
Radius	1.757 R☉
Temperature	5640 K
Metallicity	-0.11
Kepler-38B
Mass	0.249 M☉
Radius	0.2724 R☉
Metallicity	-0.11
Other designations
KOI-1740, KIC 6762829, 2MASS J19071928+4216451[5]
Database references
SIMBAD	data
KIC	data

Planetary system

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.

It is likely that additional planets in the habitable zone exist, including rocky terrestrial planets, according to simulations of the formation of the Kepler-38 system; furthermore, the orbits of any such planets are probably stable.^[6]

The Kepler-38 planetary system

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	—	0.4644	105.595	—	—	0.39 RJ

See also

• Kepler-16
• Kepler-34
• Kepler-35