Gamma Velorum

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γ2 Velorum
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 + O7.5III[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
[6] pc
Absolute magnitude (MV)−4.23 + −5.63[6]
Mass9.0 ± 0.6[6] M
Radius6 ± 3[6] R
Diameter6 ± 3[6] D
Luminosity (bolometric)170,000[6] L
Temperature57,000[7] K
Age3.5[8] -5.5[9] Myr
Mass28.5 ±1.1[6] M
Radius17 ± 2[6] R
Luminosity (bolometric)280,000[6] L
Temperature35,000[7] K
Age3.5[8]-5.5[9] Myr
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 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[11]
Declination –47° 20′ 43.027″[11]
Apparent magnitude (V) 4.27[12]
Spectral type B2III[8]
U−B color index −0.92[12]
B−V color index −0.22[12]
Radial velocity (Rv)+9.7 ± 1[12] km/s
Proper motion (μ) RA: –0.6[13] mas/yr
Dec.: +9.7[13] mas/yr
Absolute magnitude (MV)−3.62[8]
Mass14[8] M
Age8[8] 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 a combined magnitude +1.7, it is one of the brightest stars in the night sky, and contains the closest and brightest Wolf-Rayet star. It has the traditional name Regor, but is not approved by the International Astronomical Union. "Regor" is backwards for "Roger", in honor of the astronaut Roger Chaffee, who died in a fire.

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


Location of γ Velorum (circled)
Red circle.svg
Location of γ Velorum (circled)

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.[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.[8] 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.[8] 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.[8]


  1. 1.0 1.1 1.2 1.3 1.4 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. 2.0 2.1 2.2 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. 3.0 3.1 Samus, N. N.Expression error: Unrecognized word "etal". (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. Roche, P. F.; Colling, M. D.; Barlow, M. J. (2012). "The outer wind of γ Velorum". Monthly Notices of the Royal Astronomical Society 427: 581. arXiv:1208.6016. Bibcode 2012MNRAS.427..581R. doi:10.1111/j.1365-2966.2012.22005.x.
  5. 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.
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 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. 7.0 7.1 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.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 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.
  9. 9.0 9.1 9.2 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.
  10. Schmutz, W.; Schweickhardt, J.; Stahl, O.; Wolf, B.; Dumm, T.; Gang, Th.; Jankovics, I.; Kaufer, A. et al. (1997). "The orbital motion of gamma^2 Velorum". Astronomy and Astrophysics 328: 219. Bibcode 1997A&A...328..219S.
  11. 11.0 11.1 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.
  12. 12.0 12.1 12.2 12.3 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.
  13. 13.0 13.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (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. 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.