Gamma Velorum

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Gamma2 Velorum A/B
Location of Gamma Velorum
Cercle rouge 100%.svg

Gamma Velorum (circled) in the constellation Vela.
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 09m 31.95013s[1]
Declination –47° 20′ 11.7108″[1]
Apparent magnitude (V) 1.78/4.27
Spectral type WC8 + O7.5[2]
U−B color index –0.94[3]
B−V color index –0.25[3]
Variable type Wolf-Rayet
Radial velocity (Rv) +35[4] 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
[5] pc
Absolute magnitude (MV) -4.33/-5.63[5]
Mass 9/30[6] M
Luminosity (bolometric) 150,000[6] L
Age 5.5[6] Myr
Other designations
Regor, Suhail, Suhail Al-Muhlif, CD −46° 3846/3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504.
Database references

Gamma Velorum (γ Vel, γ Velorum) is a star system in the constellation Vela. At magnitude +1.7, it is one of the brightest stars in the night sky. 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, which was invented as a practical joke by the Apollo 1 astronaut Gus Grissom for his fellow astronaut Roger Chaffee.[7] 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".[8]


The Gamma Velorum system is composed of at least four stars. The brightest member, γ² Velorum or γ Velorum A, is actually 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). The binary has an orbital period of 78.5 days and separation of 1 AU. 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.[9] Its nearest companion, 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 B2III. It is separated from the Wolf-Rayet binary by 41.2", and the separation can easily be resolved with binoculars.[10]

Gamma Velorum has several fainter companions that share a common motion and are likely to be members of the Vela OB2 association.[10] 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.[10]


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".

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

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. ^ 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. 
  3. ^ a b 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 
  4. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington (Washington: Carnegie Institution of Washington): 0, Bibcode:1953QB901.W495..... 
  5. ^ a b 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. 
  6. ^ 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.  edit
  7. ^ Apollo 15 Lunar Surface Journal, Post-landing Activities, commentary at 105:11:33
  8. ^ Hoffleit. "The Bright Star Catalogue" (5th Revised ed.). Retrieved 2007-08-08. 
  9. ^ 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. 
  10. ^ a b c 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.  edit