Omicron2 Centauri

{{Short description|Variable star in the constellation Centaurus}} {{DISPLAYTITLE:Omicron² Centauri}} {{For|other star systems with this [[Bayer designation]]|Omicron Centauri}} {{Starbox begin | name = ο² Centauri }} {{Starbox image | image = {{Location mark |image=Centaurus constellation map.svg |float=center |alt= |label= |position=right |width=280 |mark=Red circle.svg |mark_width=10 |mark_link=ο² Centauri |x=840|y=894 }} | caption = Location of ο² Cen (circled) }} {{Starbox observe | epoch = J2000.0 | constell = [[Centaurus]] | ra = {{RA|11|31|48.79955}}<ref name=dr3/> | dec = {{DEC|−59|30|56.3296}}<ref name=dr3/> | appmag_v = +5.14<ref name=ducati/> {{nowrap|(5.12 - 5.22<ref name=gcvs/>)}} }} {{Starbox character | class = A2Iae<ref name=gcvs/> | b-v = +0.49<ref name=ducati/> | u-b = −0.11<ref name=ducati/> | variable = [[Alpha Cygni variable|α Cyg]]<ref name=gcvs/> | type = [[Blue supergiant]] }} {{Starbox astrometry | radial_v = −16.8<ref name=Wilson_1953/> | prop_mo_ra = −6.976 | prop_mo_dec = +1.118 | pm_footnote = <ref name=dr3/> | parallax = 0.4665 | p_error = 0.0713 | parallax_footnote = <ref name=dr3/> | absmag_v = −7.50<ref name="Kaufer 1996"/> }} {{Starbox detail | source=<ref name="Kaufer 1996"/> | mass = 18 | radius = 131 | luminosity = 105,000 | temperature = 9,080 | metal_fe = | gravity = 1.46 | rotation = 132 days | rotational_velocity = 50 | age_gyr = }} {{Starbox catalog | names = {{odlist | B=ο² Cen | HR=4442 | HD=100262 | CD=−58°4101 | FK5=2920 | HIP=56250 | SAO=239146 | GC=15820 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = HD+100262 }} {{Starbox end}}

'''Omicron² Centauri''' is a [[star]] in the southern [[constellation]] [[Centaurus]]. Its name is a [[Bayer designation]] that is [[Romanization of Greek|Latinied]] from ο² Centauri, and abbreviated Omicron² Cen or ο² Cen. This star is visible to the [[naked eye]] with a mean [[apparent visual magnitude]] of +5.12. Based on [[stellar parallax|parallax]] measurements, it is located at a distance of approximately 7,000 [[light years]] from [[Earth]].

ο² Centauri is a white [[stellar classification|A-type]] [[blue supergiant]]. It is classified as an [[Alpha Cygni variable|Alpha Cygni type]] [[variable star]] and its brightness varies from magnitude +5.12 to +5.22 with a [[Frequency|period]] of 46.3 days. In 1996, Kaufer and colleagues calculated Omicron² Centauri to be around 136,000 times as luminous, 18 times as massive and have 131 times the diameter of the Sun.<ref name="Kaufer 1996"/>

ο² Cen forms a close naked eye pair with [[Omicron1 Centauri|ο¹ Cen]], another 5th magnitude [[supergiant]] (possibly a [[yellow hypergiant]]). Both stars are located between [[Crux]] (the Southern Cross) and the brightest yellow hypergiant in the sky, [[V382 Carinae]].

== References == <references>

<ref name=dr3>{{cite Gaia DR3|5336114548828274560}}</ref>

<ref name=SIMBAD>{{cite simbad | title=omi02 Cen | access-date=2025-12-24 }}</ref>

<ref name=ducati>{{cite journal | title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system | last=Ducati | first=J. R. | journal=CDS/ADC Collection of Electronic Catalogues | volume=2237 | year=2002 | bibcode=2002yCat.2237....0D }}</ref>

<ref name=gcvs>{{cite journal | 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 | last1=Samus | first1=N. N. | last2=Durlevich | first2=O. V. | display-authors=etal | volume=1 | year=2009 | bibcode=2009yCat....102025S }}</ref>

<ref name=Wilson_1953>{{cite book | title=General catalogue of stellar radial velocities | last=Wilson | first=Ralph Elmer | year=1953 | publisher=Carnegie Institution of Washington | bibcode=1953GCRV..C......0W }}</ref>

<ref name="Kaufer 1996">{{cite journal | title=Long-term spectroscopic monitoring of BA-type supergiants. I. Halpha_ line-profile variability | last1=Kaufer | first1=A. | last2=Stahl | first2=O. | last3=Wolf | first3=B. | last4=Gaeng | first4=T. | last5=Gummersbach | first5=C. A. | last6=Kovacs | first6=J. | last7=Mandel | first7=H. | last8=Szeifert | first8=T. | display-authors=1 | journal=Astronomy and Astrophysics | volume=305 | pages=887–901 | year=1996 | bibcode=1996A&A...305..887K }}</ref>

</references>

{{Stars of Centaurus}}

{{DEFAULTSORT:Omicron2 Centauri}} <!-- Physical properties --> [[Category:A-type supergiants]] [[Category:Alpha Cygni variables]] <!-- Constellation & catalogues --> [[Category:Centaurus]] [[Category:Bayer objects|Centauri, Omicron2]] [[Category:Bright Star Catalogue objects|4442]] [[Category:Durchmusterung objects]] [[Category:Henry Draper Catalogue objects|100262]] [[Category:Hipparcos objects|056250]]