Gliese 229
 Gliese 229 A and B. |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Lepus |
| Right ascension | 06h 10m 34.6154s |
| Declination | −21° 51′ 52.715″ |
| Apparent magnitude (V) | 8.14 |
| Characteristics | |
| Spectral type | M1Ve/T7 |
| U−B color index | +1.222 |
| B−V color index | +1.478 |
| Variable type | Flare star |
| Astrometry | |
| Radial velocity (Rv) | +3.9 km/s |
| Proper motion (μ) |
RA: –137.01 mas/yr Dec.: –714.05 mas/yr |
| Parallax (π) | 173.81 ± 0.99mas |
| Distance | 18.8 ± 0.1 ly (5.75 ± 0.03 pc) |
| Absolute magnitude (MV) | 9.33 |
| Absolute bolometric magnitude (Mbol) |
7.96 |
| Details | |
| Mass | 0.58/0.02 M☉ |
| Radius | 0.69/0.047 R☉ |
| Luminosity (bolometric) | 0.052 L☉ |
| Luminosity (visual, LV) | 0.0158/0.00032 L☉ |
| Temperature | 3,700/950 K |
| Rotational velocity (v sin i) | 1 km/s |
| Other designations | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
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.
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