# Gliese 229

Observation data Epoch J2000      Equinox J2000 Constellation Gliese 229 A and B. Lepus 06h 10m 34.6154s[1] −21° 51′ 52.715″[1] 8.14 M1Ve/T7[2] +1.222[2] +1.478[2] Flare star 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] mas Distance 18.8 ± 0.1 ly (5.75 ± 0.03 pc) Absolute magnitude (MV) 9.33[5] Absolute bolometricmagnitude (Mbol) 7.96[6] Mass 0.58/0.02[7] M☉ Radius 0.69/0.047[8] R☉ Luminosity (bolometric) 0.052[nb 1]/~0.000011 L☉ Luminosity (visual, LV) 0.0158[nb 2] L☉ Temperature 3,700[6]/950[9] K Rotational velocity (v sin i) 1[10] km/s BD-21°1377, HD 42581, HIP 29295, LHS 1827, NSV 2863, SAO 171334, TYC 5945- 765-1 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.[10]

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.[11] 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.[12] 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,[13][14] 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.[15] This object now has a surface temperature of 950 K.[9]

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)
GJ 229 Ab >32 M 0.97 471 <0.32
GJ 229B <21–52.4[8] MJ >35 >10000 0.468[8] RJ

## References

1. ^ a b c d Perryman, M. A. C.; et al. (1997). "The Hipparcos Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
2. 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 (2): 119–130. Bibcode:1985MNRAS.214..119B. doi:10.1093/mnras/214.2.119.
3. ^ 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. Bibcode:1967IAUS...30...57E. |access-date= requires |url= (help)
4. ^ Perryman; et al. (1997). "HIP 29295". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-29.
5. ^ "The One Hundred Nearest Star Systems". RECONS. Georgia State University. January 1, 2012. Retrieved 2013-04-16.
6. ^ a b Morales, J. C.; Ribas, I.; Jordi, C. (February 2008). "The effect of activity on stellar temperatures and radii". Astronomy and Astrophysics. 478 (2): 507–512. arXiv:0711.3523. Bibcode:2008A&A...478..507M. doi:10.1051/0004-6361:20078324. Data from CDS table J/A+A/478/507.
7. ^ 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. arXiv:0908.0944. Bibcode:2009A&A...505..859Z. doi:10.1051/0004-6361/200912479.
8. ^ a b c d 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. Bibcode:1989ApJS...71..895W. doi:10.1086/191401.
9. ^ a b 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. arXiv:0712.1887. Bibcode:2008A&A...480..193G. doi:10.1051/0004-6361:20078229.
10. ^ 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. arXiv:astro-ph/0702634. Bibcode:2007A&A...467..259R. doi:10.1051/0004-6361:20066991.
11. ^ Schmitt JHMM; Fleming TA; Giampapa MS (September 1995). "The X-Ray View of the Low-Mass Stars in the Solar Neighborhood". Astrophys. J. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
12. ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. 22. Bibcode:1969VeARI..22....1G.
13. ^ "Astronomers Announce First Clear Evidence of a Brown Dwarf". Space Telescope Science Institute news release STScI-1995-48. November 29, 1995. Retrieved 24 September 2013.
14. ^ Oppenheimer, Ben R. (2014), "Companions of Stars: From Other Stars to Brown Dwarfs to Planets and the Discovery of the First Methane Brown Dwarf", in Joergens, Viki, 50 Years of Brown Dwarfs - From Prediction to Discovery to Forefront of Research, Astrophysics and Space Science Library, 401, Springer, pp. 81–111, arXiv:1404.4430, doi:10.1007/978-3-319-01162-2_6, ISBN 978-3-319-01162-2
15. ^ J. Kelly Beatty; Carolyn Collins Petersen; Andrew Chaikin (1999). The New Solar System. Cambridge University Press.
16. ^ Tuomi, Mikko; et al. (2014). "Bayesian search for low-mass planets around nearby M dwarfs – Estimates for occurrence rate based on global detectability statistics". Monthly Notices of the Royal Astronomical Society. in press (2): 1545. arXiv:1403.0430. Bibcode:2014MNRAS.441.1545T. doi:10.1093/mnras/stu358.

## Notes

1. ^ Using the absolute bolometric magnitude of Gliese 229 A ${\displaystyle \scriptstyle M_{bol_{\ast }}=7.96}$ and the absolute bolometric magnitude of the Sun ${\displaystyle \scriptstyle M_{bol_{\odot }}=4.74}$, the bolometric luminosity can be calculated by ${\displaystyle \scriptstyle {\frac {L_{bol_{\ast }}}{L_{bol_{\odot }}}}=10^{0.4\left(M_{bol_{\odot }}-M_{bol_{\ast }}\right)}}$
2. ^ Using the absolute visual magnitude of Gliese 229 A ${\displaystyle \scriptstyle M_{V_{\ast }}=9.33}$ and the absolute visual magnitude of the Sun ${\displaystyle \scriptstyle M_{V_{\odot }}=4.83}$, the visual luminosity can be calculated by ${\displaystyle \scriptstyle {\frac {L_{V_{\ast }}}{L_{V_{\odot }}}}=10^{0.4\left(M_{V_{\odot }}-M_{V_{\ast }}\right)}}$