Epoch J2000 Equinox J2000
|Right ascension||06h 10m 34.6154s|
|Declination||−21° 51′ 52.715″|
|Apparent magnitude (V)||8.14|
|U−B color index||+1.222|
|B−V color index||+1.478|
|Variable type||Flare star|
|Radial velocity (Rv)||+3.9 km/s|
|Proper motion (μ)||RA: –137.01 mas/yr
Dec.: –714.05 mas/yr
|Parallax (π)||173.81 ± 0.99 mas|
|Distance||18.8 ± 0.1 ly
(5.75 ± 0.03 pc)
|Absolute magnitude (MV)||9.33|
|Luminosity (bolometric)||0.052[nb 1] L☉|
|Luminosity (visual, LV)||0.0158[nb 2]/0.00032 L☉|
|Rotational velocity (v sin i)||1 km/s|
Gliese 229 (also written as Gl 229 or GJ 229) is a red dwarf about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun, 69% of the Sun's radius, and a very low projected rotation velocity of 1 km/s at the stellar equator.
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. 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.
The space velocity components of this star are U = +12, V = –11 and W = –12 km/s. The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.
A substellar companion was discovered in 1994 and confirmed in 1995 as Gliese 229B, one of the first two instances of clear evidence for a brown dwarf, along with Teide 1. Although too small to sustain hydrogen-burning nuclear fusion as in a main sequence star, with a mass of 21 to 52.4 times that of Jupiter (0.02 to 0.05 solar masses), it is still too massive to be a planet. As a brown dwarf, its core temperature is high enough to initiate the fusion of deuterium with a proton to form helium-3, but it is thought that it used up all its deuterium fuel long ago. This object now has a surface temperature of 950 K.
In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229. Given the proximity to the Sun, the orbit of GJ 229b might be fully characterized by the Gaia space-astrometry mission or via direct imaging.
(in order from star)
|GJ 229 Ab||>32 M⊕||0.97||471||<0.32||—||—|
|GJ 229B||<21–52.4 MJ||>35||>00010||—||—||0.468 RJ|
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- Using the absolute bolometric magnitude of Gliese 229 A and the absolute bolometric magnitude of the Sun , the bolometric luminosity can be calculated by
- Using the absolute visual magnitude of Gliese 229 A and the absolute visual magnitude of the Sun , the visual luminosity can be calculated by
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