{{short description|Star system in the constellation Vela}} {{Starbox begin | name=γ<sup>2</sup> Velorum }} {{Starbox image | image= {{Location mark |image=Vela constellation map.svg|alt=|float=center|width=260 |label=|position=right |mark=Red circle.svg|mark_width=12|mark_link=Gamma Velorum|x=897|y=482 }} |caption=Location of γ Velorum (circled) }} {{Starbox observe | constell=Vela | epoch=J2000 | ra={{RA|08|09|31.95013}}<ref name=hipparcos>{{cite journal | first=F. | last=van Leeuwen |date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 |arxiv = 0708.1752 | s2cid=18759600 }}</ref> | dec={{DEC|−47|20|11.7108}}<ref name=hipparcos/> | appmag_v=1.83<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}}</ref> {{nowrap|(1.81–1.87<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|pages=02025|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009|display-authors=etal}}</ref>)}} }} {{Starbox character | class=WC8 + O7.5III<ref name=roche>{{cite journal|bibcode=2012MNRAS.427..581R|arxiv=1208.6016|title=The outer wind of γ Velorum|journal=Monthly Notices of the Royal Astronomical Society|volume=427|pages=581|last1=Roche|first1=P. F.|last2=Colling|first2=M. D.|last3=Barlow|first3=M. J.|year=2012|issue=1|doi=10.1111/j.1365-2966.2012.22005.x|doi-access=free |s2cid=119234167}}</ref> | b-v=−0.25<ref name=ducati/> | u-b=−0.94<ref name=ducati/> | variable=Wolf–Rayet<ref name=gcvs/> }} {{Starbox astrometry | radial_v={{val|p=+|12|1}}<ref name=niemela1980>{{cite journal|last1=Niemela|first1=V. S.|last2=Sahade|first2=J.|title=The orbital elements of Gamma 2 Velorum|journal=The Astrophysical Journal|volume=238|year=1980|pages=244|issn=0004-637X|doi=10.1086/157981|bibcode = 1980ApJ...238..244N }}</ref> | prop_mo_ra=–6.07<ref name=hipparcos/> | prop_mo_dec=+10.43<ref name=hipparcos/> | parallax=2.92 | p_error=0.30 | parallax_footnote=<ref name=hipparcos/> | dist_ly={{val|1096|26|23}}<ref name=crowther>{{Cite journal |last1=Crowther |first1=Paul A. |last2=Barlow |first2=M. J. |last3=Royer |first3=P. |last4=Hillier |first4=D. J. |last5=Bestenlehner |first5=J. M. |last6=Morris |first6=P. W. |last7=Wesson |first7=R. |date=2024-01-01 |title=Oxygen abundance of γ Vel from [O III] 88μm Herschel/PACS spectroscopy |journal=Monthly Notices of the Royal Astronomical Society |volume=528 |issue=2 |page=2026 |doi=10.1093/mnras/stae145 |issn=0035-8711|doi-access=free |arxiv=2310.15170 |bibcode=2024MNRAS.528.2026C }}</ref> | dist_pc={{val|336|8|7}} | absmag_v=−4.6 + −6.0<ref name=crowther/> }} {{Starbox orbit | reference = <ref name=schmutz>{{cite journal|bibcode=1997A&A...328..219S|title=The orbital motion of gamma^2 Velorum|journal=Astronomy and Astrophysics|volume=328|pages=219|last1=Schmutz|first1=W.|last2=Schweickhardt|first2=J.|last3=Stahl|first3=O.|last4=Wolf|first4=B.|last5=Dumm|first5=T.|last6=Gang|first6=Th.|last7=Jankovics|first7=I.|last8=Kaufer|first8=A.|last9=Lehmann|first9=H.|last10=Mandel|first10=H.|last11=Peitz|first11=J.|last12=Rivinius|first12=Th.|year=1997}}</ref> | primary = O | name = WR | period = | period_unitless = {{val|78.53|0.01}} days | axis = | axis_unitless = 1.2<ref name=north/> AU | eccentricity = {{val|0.326|0.01}} | inclination = {{val|65|8}} | periarg = {{val|248|4}} | periastron = {{val|fmt=commas|2,450,120.5|2}} | periarg_primary = | k1 = {{val|38.4|2}} | k2 = {{val|122|2}} }} {{Starbox detail | component1 = WR | mass = {{val|9.0|0.6}}<ref name=north>{{cite journal|bibcode=2007MNRAS.377..415N|title=Γ2 Velorum: Orbital solution and fundamental parameter determination with SUSI|journal=Monthly Notices of the Royal Astronomical Society|volume=377|pages=415–424|last1=North|first1=J. R.|last2=Tuthill|first2=P. G.|last3=Tango|first3=W. J.|last4=Davis|first4=J.|date=2007|issue=1|doi=10.1111/j.1365-2966.2007.11608.x|doi-access=free |arxiv = astro-ph/0702375 |s2cid=16425744}}</ref> | radius = 1.9<ref name=crowther/> | temperature = 90,000<ref name=crowther/> | luminosity = | luminosity_bolometric = 204,000<ref name=crowther/> | gravity = 4.85<ref name=crowther/> | age_myr = 5<ref name=crowther/> | component2 = O | mass2 = {{val|28.5|1.1}}<ref name=north/> | radius2 = 16.2<ref name=crowther/> | temperature2 = 35,100<ref name=crowther/> | luminosity2 = | luminosity_bolometric2 = 363,000<ref name=crowther/> | gravity2 = 3.47<ref name=crowther/> | age_myr2 = 5<ref name=crowther/> }} {{Starbox catalog | names=Regor, Suhail Al-Muhlif, CD−46°3847, FK5 309, HD 68273, HIP 39953, HR 3207, SAO 219504, WR 11 }} {{Starbox reference | Simbad=HD+68273 }} {{Starbox end}}
'''Gamma Velorum''' is a double star in the constellation Vela, with each of the two stars a spectroscopic binary. 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''' {{IPAc-en|'|r|iː|g|ɔr}},<ref name=Kunitzsch>{{cite book |last1=Kunitzsch |first1=Paul |last2=Smart |first2=Tim |date = 2006 |edition = 2nd rev. |title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations |publisher = Sky Pub |location = Cambridge, Massachusetts |isbn = 978-1-931559-44-7}}</ref> but neither is approved by the International Astronomical Union, making it the brightest star by apparent magnitude without an IAU approved name.
The γ Velorum system includes a pair of stars separated by 41{{pprime}}, each of which is also a spectroscopic binary system. γ<sup>2</sup> Velorum, the brighter of the visible pair, contains the Wolf–Rayet star and a blue supergiant, while γ<sup>1</sup> Velorum contains a blue giant and an unseen companion.
==Distance== Gamma Velorum is close enough to have accurate parallax measurements as well as distance estimates by more indirect means. The ''Hipparcos'' parallax for γ<sup>2</sup> 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 {{val|368|51|u=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.<ref name=millour>{{cite journal|bibcode=2007A&A...464..107M|title=Direct constraint on the distance of γ2 Velorum from AMBER/VLTI observations|journal=Astronomy and Astrophysics|volume=464|pages=107–118|last1=Millour|first1=F.|last2=Petrov|first2=R. G.|last3=Chesneau|first3=O.|last4=Bonneau|first4=D.|last5=Dessart|first5=L.|last6=Bechet|first6=C.|last7=Tallon-Bosc|first7=I.|last8=Tallon|first8=M.|last9=Thiébaut|first9=E.|last10=Vakili|first10=F.|last11=Malbet|first11=F.|last12=Mourard|first12=D.|last13=Antonelli|first13=P.|last14=Beckmann|first14=U.|last15=Bresson|first15=Y.|last16=Chelli|first16=A.|last17=Dugué|first17=M.|last18=Duvert|first18=G.|last19=Gennari|first19=S.|last20=Glück|first20=L.|last21=Kern|first21=P.|last22=Lagarde|first22=S.|last23=Le Coarer|first23=E.|last24=Lisi|first24=F.|last25=Perraut|first25=K.|last26=Puget|first26=P.|last27=Rantakyrö|first27=F.|last28=Robbe-Dubois|first28=S.|last29=Roussel|first29=A.|last30=Tatulli|first30=E.|display-authors=29|year=2007|issue=1|doi=10.1051/0004-6361:20065408|arxiv = astro-ph/0610936 |s2cid=15349002}}</ref>
==Stellar system== [[File:Cr 173 (Vela OB2).jpg|thumb|left|Vela OB2 with γ Velorum being the brightest star in the upper left. The image also shows the smaller star cluster NGC 2547 in the lower left part. The nebulosity around the stars is part of the Gum Nebula.]] The Gamma Velorum system is composed of at least four stars. The brightest member, γ<sup>2</sup> Velorum or γ Velorum A, is a spectroscopic binary composed of a blue supergiant of spectral class O7.5 ({{Solar mass|link=y|~30}}), and a massive Wolf–Rayet star ({{Solar mass|~9}}, originally {{Solar mass|~35}}).<ref name=north/> The binary has an orbital period of 78.5 days and separation varying from 0.8 to 1.6 astronomical units. Both the Wolf–Rayet star and the blue supergiant are likely to end their lives as Type Ib supernovae; they are among the nearest supernova candidates to the Sun.<ref name=ass336_2_287>{{cite journal|bibcode=2011Ap&SS.336..287B|title=The past, present and future supernova threat to Earth's biosphere|journal=Astrophysics and Space Science|volume=336|issue=2|pages=287–302|last1=Beech|first1=Martin|date=2011|doi=10.1007/s10509-011-0873-9|s2cid=119803426}}</ref><ref>{{Cite web |title=Regor |url=http://stars.astro.illinois.edu/sow/regor.html |access-date=2024-08-18 |website=stars.astro.illinois.edu}}</ref> 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, more luminous and also more massive. For clarity, the components are now often referred to as WR and O.<ref name=north/>
γ<sup>2</sup> Velorum has been revealed as a gamma-ray emitter on the basis of Fermi measurements showing a modulation fully compliant with its orbital period.<ref>{{cite journal |last1=Martí-Devesa |first1=G. |last2=Reimer |first2=O. |last3=Li |first3=J. |last4=Torres |first4=D. F. |title=Hints of γ-ray orbital variability from γ<SUP>2</SUP> Velorum |journal=Astronomy and Astrophysics |date=2020 |volume=635 |doi=10.1051/0004-6361/202037462 |arxiv=2001.02708 |bibcode=2020A&A...635A.141M }}</ref> This discovery allows this system to be part of the category of Particle-Accelerating Colliding-Wind Binaries (PACWB),<ref>{{cite journal |last1=De Becker |first1=M. |last2=Raucq |first2=F. |title=Catalogue of particle-accelerating colliding-wind binaries |journal=Astronomy and Astrophysics |date=2013 |volume=558 |pages=A28 |doi=10.1051/0004-6361/201322074 |arxiv=1308.3149 |bibcode=2013A&A...558A..28D }}</ref><ref>{{cite web | url=https://www.astro.uliege.be/~debecker/pacwb/ | title=PACWB }}</ref> binary systems made of massive stars whose winds collide, resulting in particle acceleration.
The dimmer (apparent magnitude +4.2) γ<sup>1</sup> 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.<ref name=jeffries>{{Cite journal | doi = 10.1111/j.1365-2966.2008.14162.x| title = The stellar association around Gamma Velorum and its relationship with Vela OB2| year = 2009| last1 = Jeffries | first1 = R. D.| last2 = Naylor | first2 = T.| last3 = Walter | first3 = F. M.| last4 = Pozzo | first4 = M. P.| last5 = Devey | first5 = C. R.| journal = Monthly Notices of the Royal Astronomical Society| volume = 393| issue = 2| pages = 538| doi-access = free| arxiv = 0810.5320 |bibcode = 2009MNRAS.393..538J | s2cid = 17560818 }}</ref> 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 γ<sup>2</sup> 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.<ref name=jeffries/> 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.<ref name=jeffries/>
{{Starbox begin | name=γ<sup>1</sup> Velorum }} {{Starbox observe | epoch=J2000 | ra={{RA|08|09|29.3175}}<ref name=dr3-1/> | dec={{DEC|−47|20|43.013}}<ref name=dr3-1/> | appmag_v=4.27<ref name=hernandez1980/> | constell=Vela }} {{Starbox character | class=B2III<ref name=jeffries/> | b-v=−0.22<ref name=hernandez1980/> | u-b=−0.92<ref name=hernandez1980/> | variable= }} {{Starbox astrometry | radial_v={{val|p=+|9.7|1}}<ref name=hernandez1980>{{cite journal|last1=Hernandez|first1=C. A.|last2=Sahade|first2=J.|title=The Spectroscopic Binary GAMMA-1-VELORUM|journal=Publications of the Astronomical Society of the Pacific|volume=92|year=1980|pages=819|issn=0004-6280|doi=10.1086/130756|bibcode = 1980PASP...92..819H |s2cid=120181128 }}</ref> | prop_mo_ra=–6.243<ref name=dr3-1/> | prop_mo_dec=+9.475<ref name=dr3-1/> | parallax=2.6052 | p_error=0.1235 | parallax_footnote=<ref name=dr3-1>{{cite Gaia DR3|5519266900766220800}}</ref> | dist_pc= | absmag_v=−3.62<ref name=jeffries/> }} {{Starbox detail | mass = 14<ref name=jeffries/> | radius = {{Val|9.61|0.39}}<ref name=dr3-1/> | luminosity = 13,122<ref name=quintana2025>{{cite journal |last1=Quintana |first1=Alexis L. |last2=Wright |first2=Nicholas J. |last3=Martínez García |first3=Juan |title=A census of OB stars within 1 KPC and the star formation and core collapse supernova rates of the Milky Way |journal=Monthly Notices of the Royal Astronomical Society |date=2025 |volume=538 |issue=3 |page=1367 |doi=10.1093/mnras/staf083 |doi-access=free |arxiv=2503.08286 |bibcode=2025MNRAS.538.1367Q }}</ref> | gravity = {{Val|3.47|0.03}}<ref name=dr3-1/> | temperature = {{Val|20100|100|fmt=commas}}<ref name=dr3-1/> | metal = <!--Metallicity (no units provided by template)--> | metal_fe = <!--Metallicity ([Fe/H] dex) --> | rotation = <!--Rotation (no units provided by template)--> | rotational_velocity = <!--Rotational velocity (v sin i, in km/s)--> | age = <!--Age (in years)--> | age_myr = 8<ref name=jeffries/> | age_gyr = <!--Age (in billions of years)--> }} {{Starbox catalog | names = {{odlist | CD=−46°3846 | HD=68243 | HR=3206 | SAO=219501 }} }} {{Starbox reference | Simbad=HD+68243 }} {{Starbox end}}
==Etymology== 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.<ref name=allen>{{cite book |last = Allen |first = R. H. |author-link = Richard Hinckley Allen |date = 1963 |title = Star Names: Their Lore and Meaning |edition = rep. |publisher = Dover Publications Inc |location = New York, NY |isbn = 0-486-21079-0}}</ref>
In Chinese, {{lang|zh|天社}} ({{lang|zh-Latn|Tiān Shè}}), meaning ''Celestial Earth God's Temple'', refers to an asterism consisting of γ<sup>2</sup> Velorum,<!-- The Chinese were able to see the double star? --> δ Velorum, κ Velorum and b Velorum.<ref>{{in lang|zh}} ''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}}.</ref> Consequently, γ<sup>2</sup> Velorum itself is known as {{lang|zh|天社一}} ({{lang|zh-Latn|Tiān Shè yī}}), "the First Star of Celestial Earth God's Temple".<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20081025110153/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm |date=2008-10-25 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>
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.<ref>Apollo 15 Lunar Surface Journal, [https://apollojournals.org/alsj/a15/a15.postland.html#1051133 ''Post-landing Activities''], commentary at 105:11:33</ref>
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''.<ref name=hr>{{cite journal|bibcode=1991bsc..book.....H|title=The Bright star catalogue|journal=New Haven, Conn.: Yale University Observatory, 5th Rev.ed.|year=1991|last1=Hoffleit|first1=Dorrit|last2=Jaschek|first2=Carlos}}</ref>
==See also== * Gamma Cassiopeiae, informally named ''Navi'' for astronaut Virgil Ivan "Gus" Grissom * Iota Ursae Majoris, informally named ''Dnoces'' for astronaut Ed White
==References== {{reflist}}
{{Stars of Vela}} {{Authority control}}
<!-- Properties --> Category:O-type giants Category:B-type giants Category:Wolf–Rayet stars Category:Spectroscopic binaries 6 Category:Gum Nebula <!-- Location/Catalogues --> Category:Vela (constellation) Velorum, Gamma 3207 Category:Durchmusterung objects 068273 039953 Regor Category:Southern pole stars Category:Lucidae Category:Brightest stars