Gamma Centauri

Gamma Centauri (γ Cen, γ Centauri) is a star in the southern constellation Centaurus. It has the proper name Muhlifain,[10] not to be confused with Muliphein, which is γ Canis Majoris; both names derive from the same Arabic root.

This article is about γ Centauri. For HD 127233, see Y Centauri. For y Centauri, see HD 120987.
Gamma Centauri A/B
Location of γ Centauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension 12h 41m 31.04008s[1]
Declination −48° 57′ 35.5375″[1]
Apparent magnitude (V) +2.17[2] (+2.85/+2.95)[3]
Characteristics
Spectral type A1IV+[4] (A0III/A0III)[5]
U−B color index −0.01[2]
B−V color index −0.01[2]
Astrometry
Radial velocity (Rv)−5.5[6] km/s
Proper motion (μ) RA: −185.72[1] mas/yr
Dec.: +5.79[1] mas/yr
Parallax (π)25.06 ± 0.28[1] mas
Distance130 ± 1 ly
(39.9 ± 0.4 pc)
Absolute magnitude (MV)–0.81[5]
Orbit[7][8]
Companionγ Centauri B
Period (P)83.57 yr
Semi-major axis (a)0.869″
Eccentricity (e)0.793
Inclination (i)113.7°
Longitude of the node (Ω)2.6°
Periastron epoch (T)1931.25
Argument of periastron (ω)
(secondary)		187.9°
Details
Mass2.91[9] M☉
Surface gravity (log g)3.52[4] cgs
Temperature9,082[4] K
Other designations
Muhlifain, HR 4819, HD 110304, CD−48°7597, SAO 223603, WDS 12415-4858, HIP 61932, GC 17262, CCDM J12415-4858.
Database references
SIMBADdata

It is a binary star system about 130 light-years (40 parsecs) from Earth. The combined apparent visual magnitude of the pair is +2.17;[2] individually they are third magnitude stars.[3] The stellar classification of the pair is A1IV+,[4] suggesting they are A-type subgiant stars in the process of becoming giants. Individually, their stellar classifications are sometimes listed as A0III, which would mean they have already become giants.[5]

In 2000, the pair had an angular separation of 1.217 arcseconds with a position angle of 351.9°.[3] Their positions have been observed since 1897, which is long enough to estimate an orbital period of 84.5 years and a semimajor axis of 0.93 arcseconds.[7] At the distance of this system, this is equivalent to a linear distance of about 93 Astronomical Units.[11] The star Tau Centauri is relatively close to Gamma Centauri, with an estimated separation of 1.72 light-years (0.53 pc).[9]

Etymology

In Chinese astronomy, 庫樓 (Kù Lóu), meaning Arsenal, refers to an asterism consisting of γ Centauri, ζ Centauri, η Centauri, θ Centauri, 2 Centauri, HD 117440, ξ1 Centauri, τ Centauri, D Centauri and σ Centauri.[12] Consequently, the Chinese name for γ Centauri itself is 庫樓七 (Kù Lóu qī, English: the Seventh Star of Arsenal.)[13]

The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named Iritjinga, "The Eagle-hawk", a quadrangular arrangement comprising this star, δ Cen (Ma Wei), δ Cru (Imai) and γ Cru (Gacrux).[14]

References
  1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  3. Fabricius, C.; Makarov, V. V. (April 2000). "Two-colour photometry for 9473 components of close Hipparcos double and multiple stars". Astronomy and Astrophysics. 356: 141–145. Bibcode:2000A&A...356..141F.
  4. Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637.
  5. Schaaf, Fred (2008). The brightest stars: discovering the universe through the sky's most brilliant stars. The Brightest Stars: Discovering the Universe through the Sky's Most Brilliant Stars. John Wiley and Sons. p. 262. Bibcode:2008bsdu.book.....S. ISBN 0-471-70410-5.
  6. Evans, D. S. (June 20–24, 1966). Batten, Alan Henry; Heard, John Frederick (eds.). The Revision of the General Catalogue of Radial Velocities. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  7. Mason, Brian D.; et al. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  8. "Sixth Catalog of Orbits of Visual Binary Stars".
  9. Shaya, Ed J.; Olling, Rob P. (January 2011). "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue". The Astrophysical Journal Supplement. 192 (1): 2. arXiv:1007.0425. Bibcode:2011ApJS..192....2S. doi:10.1088/0067-0049/192/1/2.
  10. Paul Kunitzsch (1959). Arabische Sternnamen in Europa, von Paul Kunitzsch. O. Harrassowitz. p. 188.
  11. Kaler, James B. "MUHLIFAIN (Gamma Centauri)". Stars. University of Illinois. Retrieved 2011-12-31.
  12. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 30, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  14. Raymond Haynes; Roslynn D. Haynes; David Malin; Richard McGee (1996), Explorers of the Southern Sky: A History of Australian Astronomy, Cambridge: Cambridge University Press, p. 8, ISBN 978-0-521-36575-8
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