Kepler-28

Kepler-28 is an M-type main-sequence star about 1,450 light-years (440 parsecs) away in the northern constellation of Cygnus.^[2] With an apparent visual magnitude of 15.036,^[3] this star is too faint to be seen with the naked eye. It is orbited by two exoplanets.

Kepler-28

Kepler-28 compared to the Sun
Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus[1]
Right ascension	19h 28m 32.8905s[2]
Declination	+42° 25′ 45.959″[2]
Apparent magnitude (V)	15.036[3]
Characteristics
Spectral type	M0V[4]
Astrometry
Radial velocity (Rv)	−26.99±6.00[2] km/s
Proper motion (μ)	RA: −0.463(21) mas/yr[2] Dec.: 11.691(21) mas/yr[2]
Parallax (π)	2.2537±0.0185 mas[2]
Distance	1,450 ± 10 ly (444 ± 4 pc)
Details
Mass	0.684±0.026[5] M☉
Radius	0.664±0.013[5] R☉
Temperature	4499±75[5] K
Metallicity [Fe/H]	−0.17±0.11[4] dex
Rotation	17.951±0.016 days[6]
Rotational velocity (v sin i)	0.6[3] km/s
Age	2.2[7] Gyr
Other designations
KOI-870, KIC 6949607, 2MASS J19283288+4225459[8]
Database references
SIMBAD	data
KIC	data

Planetary system

The two transiting planets of Kepler-28 were discovered in 2011 using the Kepler space telescope, and were confirmed in early 2012.^[9] They are both warm sub-Neptune gas planets.^[7] The planetary parameters were updated in 2023, with lower values for all of mass, radius, and density compared to previous estimates.^[5]

The Kepler-28 planetary system^[4][5]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	1.63+0.51 −0.40 M🜨	0.062	5.91213(17)	<0.08	—	1.959+0.043 −0.042 R🜨
c	2.06+0.70 −0.52 M🜨	0.081	8.98597(27)	0.017+0.023 −0.014	—	1.857±0.042 R🜨