 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[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) | 173.19 ± 1.12[1] mas |
| Distance | 18.8 ± 0.1 ly (5.77 ± 0.04 pc) |
| Absolute magnitude (MV) | 9.33 |
| Details | |
| Mass | 0.58[4] M☉ |
| Radius | 0.69[5] R☉ |
| Temperature | 3,700[6] K |
| Rotational velocity (v sin i) | 1[7] km/s |
| Other designations | |
Gliese 229 (also written as Gl 229 or GJ 229) is a red dwarf star about 19 light years away in the constellation Lepus. It has 58% of the mass of the Sun,[4] 69% of the Sun's radius,[5] and a very low projected rotation velocity of 1 km/s at the stellar equator.[7]
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.[2]
In 1994 a substellar companion was imaged and in 1995 it was confirmed. Gliese 229B is a brown dwarf orbiting the star; although it is too small to sustain hydrogen-burning nuclear fusion, with a mass of 20 to 50 times that of Jupiter it is still too massive to be a planet. Gliese 229B was the first confirmed substellar mass object. This object has a surface temperature of 950 K.[8]
The space velocity components of this star are U = +12, V = –11 and W = –12 km/s.[9] The orbit of this star through the Milky Way galaxy has an eccentricity of 0.07 and an orbital inclination of 0.005.[2]
References
- ^ a b c d e Perryman, M. A. C. et al (1997). "The Hipparcos Catalogue". Astronomy and Astrophysics 323: L49–L52. Bibcode: 1997A&A...323L..49P.
- ^ a b c d e Byrne, P. B.; Doyle, J. G.; Menzies, J. W. (May 1, 1985). "Optical photometry and spectroscopy of the flare star Gliese 229 (=HD42581)". Monthly Notices of the Royal Astronomical Society 214: 119–130. Bibcode: 1985MNRAS.214..119B.
- ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". in Batten, Alan Henry; Heard, John Frederick. Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. http://adsabs.harvard.edu/abs/1967IAUS...30...57E. Retrieved 2009-10-19.
- ^ a b Zechmeister, M.; Kürster, M.; Endl, M. (October 2009). "The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs". Astronomy and Astrophysics 505 (2): 859-871. doi:.
- ^ a b White, Stephen M.; Jackson, Peter D.; Kundu, Mukul R. (December 1989). "A VLA survey of nearby flare stars". Astrophysical Journal Supplement Series 71: 895-904. doi:.
- ^ Morales, J. C.; Ribas, I.; Jordi, C. (February 2008). "The effect of activity on stellar temperatures and radii". Astronomy and Astrophysics (2): 507–512. doi:. Data from CDS table J/A+A/478/507.
- ^ a b Reiners, A. (May 2007). "The narrowest M-dwarf line profiles and the rotation-activity connection at very slow rotation". Astronomy and Astrophysics 467 (1): 259–268. doi:.
- ^ Geißler, K.; Chauvin, G.; Sterzik, M. F. (March 2008). "Mid-infrared imaging of brown dwarfs in binary systems". Astronomy and Astrophysics 480 (1): 193–198. doi:.
- ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. Bibcode: 1969VeARI..22....1G.
External links
- Astronomers Announce First Clear Evidence of a Brown Dwarf – STScI news release STScI-1995-48 (November 29, 1995)
- Brown dwarfs (NASA)
- Extrasolar Visions – Gliese 229
- Extrasolar Visions – Gliese 229 b
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