Gliese 229

Gliese 229
	; Gliese 229 A and B
Observation data; Epoch J2000 Equinox J2000
Constellation	Lepus
Right ascension	06h 10m 34.61494s
Declination	−21° 51′ 52.6564″
Apparent magnitude (V)	8.14
Characteristics
Evolutionary stage	Main sequence / Brown dwarf
Spectral type	M1Ve / T7
U−B color index	+1.222
B−V color index	+1.478
Variable type	Flare star
Astrometry
Radial velocity (Rv)	4.23±0.12 km/s
Proper motion (μ)	RA: −135.692(11) mas/yr ; Dec.: −719.178(17) mas/yr
Parallax (π)	173.5740 ± 0.0170 mas
Distance	18.791 ± 0.002 ly ; (5.7612 ± 0.0006 pc)
Absolute magnitude (MV)	9.326
Absolute bolometric; magnitude (Mbol)	7.96
Orbit
Companion	Gliese 229 B
Period (P)	216.925+10.604; −10.352 yr
Semi-major axis (a)	28.933+1.008; −1.000 AU
Eccentricity (e)	0.853±0.002
Inclination (i)	5.497+0.153; −0.162°
Longitude of the node (Ω)	145.946+0.306; −0.294°
Periastron epoch (T)	2466912+97; −63
Argument of periastron (ω); (secondary)	358.285+0.836; −0.846°
Semi-amplitude (K1); (primary)	0.081674+0.001688; −0.001680 km/s
Details
A
Mass	0.579 M☉
Radius	0.69 R☉
Luminosity (bolometric)	0.0430 L☉
Luminosity (visual, LV)	0.0158 L☉
Temperature	3,700 K
Rotation	27.3±0.2 d
Rotational velocity (v sin i)	1 km/s
B
Mass	60.423+2.339; −2.379 MJup
Radius	1.105±0.025 RJup
Luminosity (bolometric)	~0.000011 L☉
Surface gravity (log g)	4.93+0.02; −0.03 cgs
Temperature	869+5; −7 K
Other designations
	NSV 2863, BD−21°1377, GJ 229, HD 42581, HIP 29295, SAO 171334, LHS 1827, TYC 5945-765-1
Database references
SIMBAD	A
	B
	Gliese 229 Location of Gliese 229 in the constellation Lepus;

Gliese 229 (also written as Gl 229 or GJ 229) is a binary system composed of a red dwarf and the second brown dwarf seen by astronomers, 18.8 light years away in the constellation Lepus. The primary component has 58% of the mass of the Sun,^[3] 69% of the Sun's radius,^[6] and a very low projected rotation velocity of 1 km/s at the stellar equator.^[8]

The star is known to be a low activity flare star, which means it undergoes random increases in luminosity because of magnetic activity at the surface. The spectrum shows emission lines of calcium in the H and K bands. The emission of X-rays has been detected from the corona of this star.^[10] These may be caused by magnetic loops interacting with the gas of the star's outer atmosphere. No large-scale star spot activity has been detected.^[2]

The space velocity components of this star are U = +12, V = –11 and W = –12 km/s.^[11] The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.^[2]

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Observation data Epoch J2000 Equinox J2000
Gliese 229 A and B
Constellation	Lepus
Right ascension	06^h 10^m 34.61494^s^[1]
Declination	−21° 51′ 52.6564″^[1]
Apparent magnitude (V)	8.14
Characteristics
Evolutionary stage	Main sequence / Brown dwarf
Spectral type	M1Ve / T7^[2]
U−B color index	+1.222^[2]
B−V color index	+1.478^[2]
Variable type	Flare star
Astrometry

Radial velocity (R_v)	4.23±0.12^[1] km/s
Proper motion (μ)	RA: −135.692(11) mas/yr^[1] Dec.: −719.178(17) mas/yr^[1]
Parallax (π)	173.5740 ± 0.0170 mas^[1]
Distance	18.791 ± 0.002 ly (5.7612 ± 0.0006 pc)
Absolute magnitude (M_V)	9.326^[3]
Absolute bolometric magnitude (M_bol)	7.96^[4]

Orbit^[3]^[5]
Companion	Gliese 229 B
Period (P)	216.925+10.604 −10.352 yr
Semi-major axis (a)	28.933+1.008 −1.000 AU
Eccentricity (e)	0.853±0.002
Inclination (i)	5.497+0.153 −0.162°
Longitude of the node (Ω)	145.946+0.306 −0.294°
Periastron epoch (T)	2466912+97 −63
Argument of periastron (ω) (secondary)	358.285+0.836 −0.846°
Semi-amplitude (K₁) (primary)	0.081674+0.001688 −0.001680 km/s
Details
A
Mass	0.579^[3] `M`_☉
Radius	0.69^[6] `R`_☉
Luminosity (bolometric)	0.0430^[3] `L`_☉
Luminosity (visual, L_V)	0.0158^{[nb 1]} `L`_☉
Temperature	3,700^[4] K
Rotation	27.3±0.2 d^[7]
Rotational velocity (v sin i)	1^[8] km/s
B
Mass	60.423+2.339 −2.379^[5] M_Jup
Radius	1.105±0.025^[9] R_Jup
Luminosity (bolometric)	~0.000011 `L`_☉
Surface gravity (log g)	4.93+0.02 −0.03^[9] cgs
Temperature	869⁺⁵ ₋₇^[9] K
Other designations
NSV 2863, BD−21°1377, GJ 229, HD 42581, HIP 29295, SAO 171334, LHS 1827, TYC 5945-765-1
Database references
SIMBAD	A
	B
Gliese 229 Location of Gliese 229 in the constellation Lepus