Gamma Velorum

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Gamma Velorum is a quadruple star system in the constellation Vela. This name is the Bayer designation for the star, which is Latinised from γ Velorum and abbreviated γ Vel. At a combined magnitude of +1.72, it is one of the brightest stars in the night sky, and contains by far the closest and brightest Wolf–Rayet star. It has the traditional name Suhail al Muhlif and the modern name Regor /ˈrɡɔːr/,[1] but neither is approved by the International Astronomical Union, this makes it the brightest star by apparent magnitude to remain without an IAU approved name.

γ2 Velorum
Location of γ Velorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 31.95013s[2]
Declination –47° 20′ 11.7108″[2]
Apparent magnitude (V) 1.83[3] (1.81–1.87[4])
Spectral type WC8 + O7.5III[5]
U−B color index −0.94[3]
B−V color index −0.25[3]
Variable type Wolf–Rayet[4]
Radial velocity (Rv)+12 ± 1[6] km/s
Proper motion (μ) RA: –6.07[2] mas/yr
Dec.: +10.43[2] mas/yr
Parallax (π)2.92 ± 0.30 mas[2]
[7] pc)
Absolute magnitude (MV)−4.6 + −6.0 [7]
Period (P)78.53 ± 0.01 days
Semi-major axis (a)1.2[9] AU
Eccentricity (e)0.326 ± 0.01
Inclination (i)65 ± 8°
Periastron epoch (T)2,450,120.5 ± 2
Argument of periastron (ω)
248 ± 4°
Semi-amplitude (K1)
38.4 ± 2 km/s
Semi-amplitude (K2)
122 ± 2 km/s
Mass9.0 ± 0.6 [9] M
Radius1.9[7] R
Luminosity (bolometric)204,000[7] L
Luminosity (visual, LV)5,900[7] L
Temperature90,000[7] K
Age5[7] Myr
Mass28.5 ± 1.1[9] M
Radius16.2[7] R
Luminosity (bolometric)363,000[7] L
Luminosity (visual, LV)21,500[7] L
Temperature35,100[7] K
Age5[7] Myr
Other designations
Regor, Suhail Al-Muhlif, CD−46°3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504, WR 11
Database references
γ1 Velorum
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 29.3260s[10]
Declination –47° 20′ 43.027″[10]
Apparent magnitude (V) 4.27[11]
Spectral type B2III[12]
U−B color index −0.92[11]
B−V color index −0.22[11]
Radial velocity (Rv)+9.7 ± 1[11] km/s
Proper motion (μ) RA: –0.6[13] mas/yr
Dec.: +9.7[13] mas/yr
Absolute magnitude (MV)−3.62[12]
Mass14[12] M
Age8[12] Myr
Other designations
CD−46°3846, HD 68243, HR 3206, SAO 219501
Database references

The γ Velorum system includes a pair of stars separated by 41″, each of which is also a spectroscopic binary system. γ2 Velorum, the brighter of the visible pair, contains the Wolf–Rayet star and a blue supergiant, while γ1 Velorum contains a blue giant and an unseen companion.


Gamma Velorum is close enough to have accurate parallax measurements as well as distance estimates by more indirect means. The Hipparcos parallax for γ2 implies a distance of 342 parsecs (pc). A dynamical parallax derived from calculations of the orbital parameters gives a value of 336 pc, similar to spectrophotometric derivations. A VLTI-based interferometry measurement of the distance gives a slightly larger value of 368 ± 51 pc. All these distances are somewhat less than the commonly assumed distance of 450 pc for the Vela OB2 association which is the closest grouping of young massive stars.[14]

Stellar system[edit]

The Gamma Velorum system is composed of at least four stars. The brightest member, γ2 Velorum or γ Velorum A, is a spectroscopic binary composed of a blue supergiant of spectral class O7.5 (~30 M), and a massive Wolf–Rayet star (~9 M, originally ~35 M).[9] The binary has an orbital period of 78.5 days and separation varying from 0.8 to 1.6 astronomical units. The Wolf–Rayet star is likely to end its life in a Type Ib supernova explosion; it is one of the nearest supernova candidates to the Sun.[15] The Wolf–Rayet star has traditionally been regarded as the primary since its emission lines dominate the spectrum, but the O star is visually brighter and also more luminous. For clarity, the components are now often referred to as WR and O.[9]

The bright (apparent magnitude +4.2) γ1 Velorum or γ Velorum B, is a spectroscopic binary with a period of 1.48 days. Only the primary is detected and it is a blue-white giant. It is separated from the Wolf–Rayet binary by 41.2″, easily resolved with binoculars.[12] The pair are too close to be separated without optical assistance, and they appear to the naked eye as a single star of apparent magnitude 1.72 (at the average brightness of γ2 of 1.83).

Gamma Velorum has several fainter companions that share a common motion and are likely to be members of the Vela OB2 association.[12] The magnitude +7.3 CD-46 3848 is a white F0 star at is 62.3 arcseconds from the A component. At 93.5 arcseconds is another binary star, an F0 star of magnitude +9.2.

Gamma Velorum is associated with several hundred pre-main-sequence stars within less than a degree. The ages of these stars would be at least 5 million years.[12]


The Arabic name is al Suhail al Muḥlīf. al Muhlif refers to the oath-taker, and al Suhail is originally derived from a word meaning the plain. Suhail is used for at least three other stars: Canopus, λ Velorum (al Suhail al Wazn) and ζ Puppis (Suhail Hadar). Suhail is also a common Arabic male first name.[16]

In Chinese, 天社 (Tiān Shè), meaning Celestial Earth God's Temple, refers to an asterism consisting of γ2 Velorum, δ Velorum, κ Velorum and b Velorum.[17] Consequently, γ2 Velorum itself is known as 天社一 (Tiān Shè yī), "the First Star of Celestial Earth God's Temple".[18]

The name Regor ("Roger" spelled in reverse) was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee.[19]

Due to the exotic nature of its spectrum (bright emission lines in lieu of dark absorption lines) it is also dubbed the Spectral Gem of Southern Skies.[20]

See also[edit]


  1. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  2. ^ a b c d e 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, S2CID 18759600
  3. ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
  4. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S.
  5. ^ Roche, P. F.; Colling, M. D.; Barlow, M. J. (2012). "The outer wind of γ Velorum". Monthly Notices of the Royal Astronomical Society. 427 (1): 581. arXiv:1208.6016. Bibcode:2012MNRAS.427..581R. doi:10.1111/j.1365-2966.2012.22005.x. S2CID 119234167.
  6. ^ Niemela, V. S.; Sahade, J. (1980). "The orbital elements of Gamma 2 Velorum". The Astrophysical Journal. 238: 244. Bibcode:1980ApJ...238..244N. doi:10.1086/157981. ISSN 0004-637X.
  7. ^ a b c d e f g h i j k l Crowther, Paul A.; Barlow, M. J.; Royer, P.; Hillier, D. J.; Bestenlehner, J. M.; Morris, P. W.; Wesson, R. (2024-01-01). "Oxygen abundance of γ Vel from [O III] 88μm Herschel/PACS spectroscopy". Monthly Notices of the Royal Astronomical Society. doi:10.1093/mnras/stae145. ISSN 0035-8711.
  8. ^ Schmutz, W.; Schweickhardt, J.; Stahl, O.; Wolf, B.; Dumm, T.; Gang, Th.; Jankovics, I.; Kaufer, A.; Lehmann, H.; Mandel, H.; Peitz, J.; Rivinius, Th. (1997). "The orbital motion of gamma^2 Velorum". Astronomy and Astrophysics. 328: 219. Bibcode:1997A&A...328..219S.
  9. ^ a b c d e North, J. R.; Tuthill, P. G.; Tango, W. J.; Davis, J. (2007). "Γ2 Velorum: Orbital solution and fundamental parameter determination with SUSI". Monthly Notices of the Royal Astronomical Society. 377 (1): 415–424. arXiv:astro-ph/0702375. Bibcode:2007MNRAS.377..415N. doi:10.1111/j.1365-2966.2007.11608.x. S2CID 16425744.
  10. ^ a b Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
  11. ^ a b c d Hernandez, C. A.; Sahade, J. (1980). "The Spectroscopic Binary GAMMA-1-VELORUM". Publications of the Astronomical Society of the Pacific. 92: 819. Bibcode:1980PASP...92..819H. doi:10.1086/130756. ISSN 0004-6280. S2CID 120181128.
  12. ^ a b c d e f g Jeffries, R. D.; Naylor, T.; Walter, F. M.; Pozzo, M. P.; Devey, C. R. (2009). "The stellar association around Gamma Velorum and its relationship with Vela OB2". Monthly Notices of the Royal Astronomical Society. 393 (2): 538. arXiv:0810.5320. Bibcode:2009MNRAS.393..538J. doi:10.1111/j.1365-2966.2008.14162.x. S2CID 17560818.
  13. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
  14. ^ Millour, F.; Petrov, R. G.; Chesneau, O.; Bonneau, D.; Dessart, L.; Bechet, C.; Tallon-Bosc, I.; Tallon, M.; Thiébaut, E.; Vakili, F.; Malbet, F.; Mourard, D.; Antonelli, P.; Beckmann, U.; Bresson, Y.; Chelli, A.; Dugué, M.; Duvert, G.; Gennari, S.; Glück, L.; Kern, P.; Lagarde, S.; Le Coarer, E.; Lisi, F.; Perraut, K.; Puget, P.; Rantakyrö, F.; Robbe-Dubois, S.; Roussel, A.; et al. (2007). "Direct constraint on the distance of γ2 Velorum from AMBER/VLTI observations". Astronomy and Astrophysics. 464 (1): 107–118. arXiv:astro-ph/0610936. Bibcode:2007A&A...464..107M. doi:10.1051/0004-6361:20065408. S2CID 15349002.
  15. ^ Beech, Martin (2011). "The past, present and future supernova threat to Earth's biosphere". Astrophysics and Space Science. 336 (2): 287–302. Bibcode:2011Ap&SS.336..287B. doi:10.1007/s10509-011-0873-9. S2CID 119803426.
  16. ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (rep. ed.). New York, NY: Dover Publications Inc. ISBN 0-486-21079-0.
  17. ^ (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.
  18. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  19. ^ Apollo 15 Lunar Surface Journal, Post-landing Activities, commentary at 105:11:33
  20. ^ Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven, Conn.: Yale University Observatory, 5th Rev.ed.