Gliese 229

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Gliese 229
Brown Dwarf Gliese 229B.jpg
Gliese 229 A and B.
Observation data
Epoch J2000      Equinox J2000
Constellation Lepus
Right ascension 06h 10m 34.6154s[1]
Declination −21° 51′ 52.715″[1]
Apparent magnitude (V) 8.14
Characteristics
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 (Rv) +3.9[3] km/s
Proper motion (μ) RA: –137.01[1] mas/yr
Dec.: –714.05[1] mas/yr
Parallax (π) 173.81 ± 0.99[4]:{{{3}}} mas
Distance 18.8 ± 0.1 ly
(5.75 ± 0.03 pc)
Absolute magnitude (MV) 9.33[5]
Absolute bolometric
magnitude (Mbol)		 7.96[6]
Details
Mass 0.58/0.002[7] M☉
Radius 0.69/0.047[8] R☉
Luminosity (bolometric) 0.052[nb 1] L☉
Luminosity (visual, LV) 0.0158[nb 2]/0.00032 L☉
Temperature 3,700[6] K
Rotational velocity (v sin i) 1[9] km/s
Other designations
BD-21°1377, HD 42581, HIP 29295, LHS 1827, NSV 2863, SAO 171334, TYC 5945- 765-1
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,[7] 69% of the Sun's radius,[8] and a very low projected rotation velocity of 1 km/s at the stellar equator.[9]

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]

Substellar companions

A substellar companion was discovered in 1994 and confirmed in 1995 as Gliese 229B,[12][13] 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 20 to 50 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.[14] This object now has a surface temperature of 950 K.[15]

In March 2014, a super-Neptune mass planet candidate was announced in a much closer-in orbit around GJ 229 ([16]). 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.

The Gliese 229 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
GJ 229Ab >32 M⊕ 0.97 471 <0.32 — —
GJ 229B <80 MJ >35 >10000 — — —

References

  1. ↑ 1.0 1.1 1.2 1.3 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 Lua error in package.lua at line 80: module 'strict' not found. Data from CDS table J/A+A/478/507.
  7. ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ 8.0 8.1 Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ 9.0 9.1 Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.

Notes

  1. ↑ Using the absolute bolometric magnitude of Gliese 229 A \scriptstyle M_{bol_{\ast}}=7.96 and the absolute bolometric magnitude of the Sun \scriptstyle M_{bol_{\odot}}=4.75, the bolometric luminosity can be calculated by \scriptstyle \frac{L_{bol_{\ast}}}{L_{bol_{\odot}}}=10^{0.4\left(M_{bol_{\odot}} - M_{bol_{\ast}}\right)}
  2. ↑ Using the absolute visual magnitude of Gliese 229 A \scriptstyle M_{V_{\ast}}=9.33 and the absolute visual magnitude of the Sun \scriptstyle M_{V_{\odot}}=4.83, the visual luminosity can be calculated by \scriptstyle \frac{L_{V_{\ast}}}{L_{V_{\odot}}}=10^{0.4\left(M_{V_{\odot}} - M_{V_{\ast}}\right)}

External links

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