Gamma Velorum

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Gamma2 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
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[7] K
Age 3.5[8] -5.5[9] Myr
Mass 28.5 ±1.1[6] M
Radius 17 ± 2[6] R
Luminosity (bolometric) 280,000[6] L
Temperature 35,000[7] K
Age 3.5[8]-5.5[9] 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 Al-Muhlif, CD −46° 3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504, WR 11
Database references
Location of γ Velorum (circled)
Red circle.svg
Location of γ Velorum (circled)
Gamma1 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]
Mass 14[8] M
Age 8[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 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 name Suhail al Muhlif and the modern name Regor, but neither is approved by the International Astronomical Union.


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.[14]


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.[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]


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 γ2 Velorum, b Velorum, δ Velorum and κ 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]

γ Velorum is the South Star of Neptune.

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:0708.1752Freely accessible, 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. ^ 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:1208.6016Freely accessible. 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. ^ 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/0702375Freely accessible. Bibcode:2007MNRAS.377..415N. doi:10.1111/j.1365-2966.2007.11608.x. 
  7. ^ a b 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/0004081Freely accessible. Bibcode:2000A&A...358..187D. 
  8. ^ 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. arXiv:0810.5320Freely accessible. Bibcode:2009MNRAS.393..538J. doi:10.1111/j.1365-2966.2008.14162.x. 
  9. ^ 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:0909.0504Freely accessible. 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.; 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. 
  11. ^ 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. 
  12. ^ 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. 
  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: 107. arXiv:astro-ph/0610936Freely accessible. Bibcode:2007A&A...464..107M. doi:10.1051/0004-6361:20065408. 
  15. ^ 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. 
  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.