Gliese 163

Gliese 163 is a faint red dwarf star with multiple exoplanetary companions in the southern constellation of Dorado. Other stellar catalog names for it include HIP 19394 and LHS 188.^[10] It is too faint to be visible to the naked eye, having an apparent visual magnitude of 11.79^[2] and an absolute magnitude of 10.91.^[2] This system is located at a distance of 49.4 light-years from the Sun based on parallax measurements.^[1] Judging by its space velocity components, it is most likely a thick disk star.^[3]

Gliese 163

Observation data Epoch J2000      Equinox J2000
Constellation	Dorado
Right ascension	04h 09m 15.66834s[1]
Declination	−53° 22′ 25.2900″[1]
Apparent magnitude (V)	11.79[2]
Characteristics
Spectral type	M3.5V[3]
B−V color index	1.480±0.008[2]
Astrometry
Radial velocity (Rv)	58.30±0.24[1] km/s
Proper motion (μ)	RA: 1046.236±0.019 mas/yr[1] Dec.: 584.166±0.023 mas/yr[1]
Parallax (π)	66.0705±0.0172 mas[1]
Distance	49.36 ± 0.01 ly (15.135 ± 0.004 pc)
Absolute magnitude (MV)	10.91[2]
Details
Mass	0.405±0.010[4] M☉
Radius	0.409+0.017 −0.016[4] R☉
Luminosity	0.02163±0.00063[4] L☉
Surface gravity (log g)	4.87[5] cgs
Temperature	3,460+76 −74[4] K
Metallicity [Fe/H]	0.1±0.1[6] dex
Rotation	61.0±0.3 d[7]
Rotational velocity (v sin i)	0.85[8] km/s
Age	5[9] Gyr
Other designations
GJ 163, HIP 19394, LHS 188, LTT 1881[10]
Database references
SIMBAD	data

Planets Under a Red Sun

This is a small M-type main-sequence star with a stellar classification of M3.5V.^[3] It has a relatively low activity level for a red dwarf of its mass, suggesting it is an old star with an age of at least two billion years.^[6] This star has 41% of the mass and radius of the Sun.^[4] It is spinning slowly with a projected rotational velocity of 0.85 km/s^[8] and has a rotation period of 61 days.^[7] The star is radiating just 2%^[6] of the luminosity of the Sun from its photosphere at an effective temperature of 3,460 K.^[4]

Planetary system

In September 2012, astronomers using the HARPS instrument announced the discovery of two planets orbiting Gliese 163.^[11][12] The first planet, Gliese 163 b, is a super-Earth or mini-Neptune with an orbital period of 9 days, therefore far too hot to be considered habitable. However, Gliese 163 c, with an orbital period of 26 days and a minimum mass of 6.9 Earth masses, was considered to potentially be in the star's habitable zone, although it is hotter than Earth, with a temperature of 60 deg. C (140 deg. F). It has an eccentricity estimated to be about 0.03, giving it a fairly circular orbit. Evidence was also found for a third planet orbiting further out than c and b.^[11][12]

In June 2013, it was concluded that at least 3 planets orbit around the star with a fourth planet being a possibility,^[6] and in a paper submitted to arXiv in June 2019, that and another planet were found, thus giving the system a total of five planets.^[13]

The Gliese 163 planetary system^[14][13]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥9.9±2.3 M🜨	0.060+0.005 −0.006	8.6312+0.0023 −0.0021	0.02+0.12 −0.02	—	—
c	≥7.6+2.9 −2.3 M🜨	0.124+0.010 −0.013	25.637±0.042	0.03+0.18 −0.03	—	—
f	≥6.8±4.4 M🜨	0.326+0.027 −0.034	109.5+1.6 −1.4	0.04+0.23 −0.04	—	—
e	≥13.6+8.2 −6.5 M🜨	0.700±0.066	349+12 −10	0.03+0.25 −0.03	—	—
d	≥20.2±7.6 M🜨	1.021+0.088 −0.118	604+29 −24	0.02+0.22 −0.02	—	—