Gamma Velorum

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Gamma2 Velorum
Vela constellation map.svg
Red circle.svg

Location of γ Velorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 31.95013s[1]
Declination –47° 20′ 11.7108″[1]
Apparent magnitude (V) 1.83[2] (1.81 - 1.87[3])
Spectral type WC8 + O7.5[4]
U−B color index −0.94[2]
B−V color index −0.25[2]
Variable type Wolf-Rayet[3]
Radial velocity (Rv) +12 ± 1[5] km/s
Proper motion (μ) RA: –6.07[1] mas/yr
Dec.: +10.43[1] mas/yr
Parallax (π) 2.92 ± 0.30[1] mas
Distance 336+8
[6] pc
Absolute magnitude (MV) −4.23 + −5.63[6]
Mass 9.0 ± 0.6[6] M
Radius 6 ± 3[6] R
Luminosity (bolometric) 170,000[6] L
Temperature 57,000[4] K
Age 3.5[7] -5.5[8] Myr
Mass 28.5 ±1.1[6] M
Radius 17 ± 2[6] R
Luminosity (bolometric) 280,000[6] L
Temperature 35,000[4] K
Age 3.5[7]-5.5[8] Myr
Primary O
Companion WR
Period (P) 78.53 ± 0.01 days
Semi-major axis (a) 1.2[6] AU
Eccentricity (e) 0.326 ± 0.01
Inclination (i) 65 ± 8°
Longitude of the node (Ω) 248 ± 4°
Periastron epoch (T) 2,450,120.5 ± 2
Semi-amplitude (K1)
38.4 ± 2 km/s
Semi-amplitude (K2)
122 ± 2 km/s
Other designations
Regor, Suhail[citation needed], Suhail Al-Muhlif[citation needed], CD −46° 3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504, WR 11
Database references
Gamma1 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[7]
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[12] mas/yr
Dec.: +9.7[12] mas/yr
Absolute magnitude (MV) −3.62[7]
Mass 14[7] M
Age 8[7] Myr
Other designations
CD −46° 3846, HD 68243, HR 3206, SAO 219501
Database references

Gamma Velorum (γ Vel, γ Velorum) is a multiple star system in the constellation Vela. At magnitude +1.7, it is one of the brightest stars in the night sky, and by far the closest and brightest Wolf-Rayet star. It has the traditional names Suhail and Suhail al Muhlif, which confusingly also apply to Lambda Velorum. It also has a more modern popular name Regor.


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 pc. A dynamical parallax derived from calculations of the orbital parameters gives a value of 336 pc, similar to spectrophotometric derivations. A VLTI interferometry measurement of the distance gives a slightly larger value of 368+38
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.[13]


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).[8] 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.[14] 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.[6]

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.[7]

Gamma Velorum has several fainter companions that share a common motion and are likely to be members of the Vela OB2 association.[7] 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.

γ 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.[7]


The medieval name Suhail (Al Suhail, Alsuhail, Suhail al Muhlif, Muliphein) is short for the Arabic سهيل المحلف suhayl al-muħlif "The glorious (star) of the oath".[citation needed]

The Chinese name for the star is 天社一 (Mandarin: tiān shè yī), which means "The First Star of the Celestial Altar."[citation needed]

The name Regor was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee.[15]

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.[16]

See also[edit]


  1. ^ 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 
  2. ^ 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. 
  3. ^ 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. 
  4. ^ a b c De Marco, O.; Schmutz, W.; Crowther, P. A.; Hillier, D. J.; Dessart, L.; De Koter, A.; Schweickhardt, J. (2000). "The gamma Velorum binary system. II. WR stellar parameters and the photon loss mechanism". Astronomy and Astrophysics 358: 187. arXiv:astro-ph/0004081. Bibcode:2000A&A...358..187D. 
  5. ^ Niemela, V. S.; Sahade, J. (1980). "The orbital elements of Gamma 2 Velorum". The Astrophysical Journal 238: 244. doi:10.1086/157981. ISSN 0004-637X. 
  6. ^ a b c d e f g h i j 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: 415. arXiv:astro-ph/0702375. Bibcode:2007MNRAS.377..415N. doi:10.1111/j.1365-2966.2007.11608.x. 
  7. ^ a b c d e f g h i 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. doi:10.1111/j.1365-2966.2008.14162.x. 
  8. ^ a b c Eldridge, J. J. (2009). "A new-age determination for γ2 Velorum from binary stellar evolution models". Monthly Notices of the Royal Astronomical Society: Letters 400: L20–L23. arXiv:0909.0504. Bibcode:2009MNRAS.400L..20E. doi:10.1111/j.1745-3933.2009.00753.x. 
  9. ^ 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. 
  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. doi:10.1086/130756. ISSN 0004-6280. 
  12. ^ 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. 
  13. ^ 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: 107. Bibcode:2007A&A...464..107M. doi:10.1051/0004-6361:20065408. 
  14. ^ Beech, Martin (2011). "The past, present and future supernova threat to Earth's biosphere". Astrophysics and Space Science 336 (2): 287. Bibcode:2011Ap&SS.336..287B. doi:10.1007/s10509-011-0873-9. 
  15. ^ Apollo 15 Lunar Surface Journal, Post-landing Activities, commentary at 105:11:33
  16. ^ Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven, Conn.: Yale University Observatory, 5th rev.ed.