Kepler-89

Kepler-89 is a star with four confirmed planets. Kepler-89 is a possible wide binary star.^[5]

Kepler-89

Observation data Epoch J2000      Equinox J2000
Constellation	Cygnus
Right ascension	19h 49m 19.9343s[1]
Declination	+41° 53′ 28.006″[1]
Apparent magnitude (V)	12.4[2]
Characteristics
Spectral type	F8 V
Astrometry
Proper motion (μ)	RA: 2.063(10) mas/yr[1] Dec.: 1.337(11) mas/yr[1]
Parallax (π)	2.1069±0.0086 mas[1]
Distance	1,548 ± 6 ly (475 ± 2 pc)
Details[3]
Mass	1.25+0.03 −0.04 M☉
Radius	1.61+0.11 −0.12 R☉
Surface gravity (log g)	4.123 ± 0.055 cgs
Temperature	6116 K
Metallicity [Fe/H]	−0.01 ± 0.04 dex
Rotational velocity (v sin i)	7.33 ± 0.32 km/s
Age	3.9+0.3 −0.2 Gyr
Other designations
Gaia DR2 2076970047474270208, KOI-94, KIC 6462863, 2MASS J19491993+4153280[4]
Database references
SIMBAD	data
KIC	data

Planetary system

The discovery of four planets orbiting the star was announced October 2012 by analyzing data gathered by Kepler space telescope.^[3] Follow-up radial velocity measurements confirmed the existence of Kepler-89d, indicating that Kepler-89d is slightly larger and more massive than Saturn.^[6] In October 2013, other three planets were confirmed with Kepler-89c and Kepler-89e getting reasonable mass constraints. Transit-timing variations of the outermost planet suggest that additional planets or minor bodies are present in the system.^[7]

In 2012, a partial transit of the second outermost planet by the outermost planet was reported. This was the first time a planet-planet transit in front of the star was detected.^[8][3] This allowed to determine the mutual inclination of the planets d and e to be 1.15°.^[7]

Stephen R. Kane did a dynamical analysis of the Kepler-89 system that demonstrated that planets c and d, although close to the 2:1 secular resonance, are not permanently in a 2:1 resonance configuration.^[9]

The Kepler-89 planetary system

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	<10.5 M🜨	0.05	3.7	—	89.3°	0.13 RJ
c	7.3-11.8 M🜨	0.099	10.4	<0.1	88.36°	0.31 RJ
d	0.33±0.034 MJ	0.165	22.3	<0.1	89.871°	0.83 RJ
e	11.9-15.5 M🜨	0.298	54.3	<0.1	89.76°	0.49 RJ