View source for Astronomy:Chi2 Orionis

{{Short description|Star in the constellation Orion}}
{{DISPLAYTITLE:Chi<sup>2</sup> Orionis}}
{{other stars by Bayer designation|Chi Orionis{{!}}χ Orionis}}
{{Starbox begin
| name = [[Astronomy:Bayer designation|χ<sup>2</sup>&nbsp;Orionis]]
}}
{{Starbox image
 | image=
{{Location mark
|image=Gemini constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=χ<sup>2</sup>&nbsp;Ori|x=862|y=426
}}
|caption=Location of χ<sup>2</sup>&nbsp;Orionis (circled)
}}
{{Starbox observe
| epoch = [[Astronomy:J2000.0|J2000.0]]
| equinox = [[Astronomy:J2000.0|J2000.0]] ([[Astronomy:International Celestial Reference System|ICRS]])
| constell = [[Astronomy:Orion (constellation)|Orion]]
| ra = {{RA|06|03|55.18437}}<ref name=dr3/>
| dec = {{DEC|+20|08|18.4281}}<ref name=dr3/>
| appmag_v=4.63<ref name=crowther/><ref name=bsc1/>
}}
{{Starbox character
| class = B2Ia<ref name=crowther/>
| u-b = −0.68<ref name=bsc1/>
| b-v = +0.28<ref name=bsc1/>
| r-i = +0.22<ref name=bsc1/>
| variable = [[Astronomy:Alpha Cygni variable|α Cyg]]<ref name=gcvs2/>
}}
{{Starbox astrometry
| radial_v = {{val|16.8|0.9}}<ref name=rv/>
| prop_mo_ra = 2.679<ref name=dr3/>
| prop_mo_dec = −2.500<ref name=dr3/>
| parallax = 0.7636
| p_error = 0.1219
| parallax_footnote = <ref name=dr3/>
| absmag_v = −7.6<ref name=crowther/>
}}
{{Starbox detail
| rotational_velocity = 72<ref name=crowther/>
| radius = 61.9<ref name=crowther/>
| luminosity = 446,000<ref name=crowther/>
| mass = {{val|42.3|1.0}}<ref name="Neuhauser"/>
| gravity = 2.35<ref name=crowther/>
| temperature = 19,000<ref name=crowther/>
| age_myr = {{val|5|0.6}}<ref name="Neuhauser"/>
}}
{{Starbox catalog
| names=[[Astronomy:Bayer designation|χ<sup>2</sup>]]&nbsp;Ori, Chi<sup>2</sup>&nbsp;Orionis, Chi<sup>2</sup>&nbsp;Ori, [[Astronomy:Flamsteed designation|62]]&nbsp;Orionis, 62&nbsp;Ori, [[Astronomy:Durchmusterung|BD]]+20&nbsp;1233, [[Astronomy:Boss General Catalogue|GC]]&nbsp;7675, HD&nbsp;41117, HIP&nbsp;28716, [[Astronomy:Bright Star Catalogue|HR]]&nbsp;2135, [[Astronomy:PPM Star Catalogue|PPM]]&nbsp;95316, [[Astronomy:Smithsonian Astrophysical Observatory Star Catalog|SAO]]&nbsp;77911
}}
{{Starbox reference
| Simbad=chi2+ori
}}
{{Starbox end}}

'''Chi<sup>2</sup>&nbsp;Orionis''' ('''Chi<sup>2</sup>&nbsp;Ori''' / '''χ<sup>2</sup>&nbsp;Orionis''' / '''χ<sup>2</sup>&nbsp;Ori''') {{IPAc-en|k|aɪ|.|t|u:|'|ɒ|r|aɪ}} is a B-type [[Astronomy:Supergiant|supergiant]] [[Astronomy:Star|star]] in the [[Astronomy:Constellation|constellation]] of [[Astronomy:Orion (constellation)|Orion]].  It has an [[Astronomy:Apparent visual magnitude|apparent visual magnitude]] of 4.63 but being quite distant, and heavily [[Astronomy:Extinction|extinguished]] it burns with the greatest absolute visual light magnitude [[Astronomy:List of stars in Orion|among stars in Orion]] within the near reaches of the galaxy, 0.9 of a magnitude brighter than [[Astronomy:Rigel|Rigel]].{{cn|date=August 2022}}  Since 1943, the [[Spectrum|spectrum]] of this star has served as one of the stable anchor points by which other stars are classified.  It is considered to be a member of the Gemini OB1 [[Organization:Association|association]].<ref name=crowther/>

In apparent brightness it ranks, within Orion, admitting the higher published mean brightness of much more variable stars ranked above it, 35th.{{cn|date=August 2022}}

[[Astronomy:Chi1 Orionis|Chi<sup>1</sup>&nbsp;Orionis]] is an unrelated, yellow, main sequence star over two degrees away.

==Spectrum==
χ<sup>2</sup> Orionis has a B2 bright supergiant spectrum and is one of the standard B2 Ia stars.<ref name=baas25_1319/>  It has been reported as having unusually narrow absorption lines and some weak emission lines and was included as one of the original [[Astronomy:Be star|Be star]]s.<ref name=merrill/> It is no longer treated as a Be star since many supergiants show some emission features at high resolution and Be stars is usually defined to exclude supergiants.<ref name=andrillat/>

==Variability==
[[File:Chi2OriLightCurve.png|thumb|left|A [[Astronomy:Light curve|light curve]] for Chi<sup>2</sup> Orionis, plotted from ''Hipparcos'' data<ref name=HIPCurve/>]]
χ<sup>2</sup> Orionis was listed as having likely small amplitude variability in photometry for the Third Catalogue of Stars measured in the Geneva Observatory Photometric System, specifically varying by 22 thousandths of a magnitude.<ref name=rufener/>  It was included in the [[Astronomy:General Catalogue of Variable Stars|General Catalogue of Variable Stars]] based on [[Astronomy:Hipparcos|Hipparcos satellite]] photometry with a magnitude range (in the Hipparchos photometric system) of 4.68 - 4.72 and a period of 2.8 days.<ref name=ibvs/>  A detailed study of the Hipparcos photometry confirmed the star as an [[Astronomy:Alpha Cygni variable|α Cyg variable]] and gave the amplitude of variation as 0.057 magnitudes.<ref name=lefevre/>
{{clear left}}

==References==
{{reflist|30em|refs=

<ref name=dr3>{{cite Gaia DR3|3374836252947269888}}</ref>

<ref name=HIPCurve>{{cite web
 | title=Light Curve |url=https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve
 | website=Hipparcos ESA |publisher=ESA |access-date=11 August 2022}}</ref>

<ref name=andrillat>{{cite journal|bibcode=1994A&AS..103..135A|title=A study of Be stars in the wavelength region around Paschen 7|journal=Astronomy and Astrophysics Supplement Series |volume=103|last1=Andrillat|first1=Y.|last2=Jaschek|first2=M.|last3=Jaschek|first3=C.|year=1994}}</ref>

<ref name=rufener>{{cite journal|bibcode=1982A&AS...48..503R|title=List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry|journal=Astronomy and Astrophysics Supplement Series|volume=48|pages=503|last1=Rufener|first1=F.|last2=Bartholdi|first2=P.|year=1982}}</ref>

<ref name=ibvs>{{cite journal|bibcode=1999IBVS.4659....1K|title=The 74th Special Name-list of Variable Stars|journal=Information Bulletin on Variable Stars|volume=4659|pages=1|last1=Kazarovets|first1=E. V.|last2=Samus|first2=N. N.|last3=Durlevich|first3=O. V.|last4=Frolov|first4=M. S.|last5=Antipin|first5=S. V.|last6=Kireeva|first6=N. N.|last7=Pastukhova|first7=E. N.|year=1999}}</ref>

<ref name=lefevre>{{cite journal|bibcode=2009A&A...507.1141L|title=A systematic study of variability among OB-stars based on HIPPARCOS photometry|journal=Astronomy and Astrophysics|volume=507|issue=2|pages=1141|last1=Lefèvre|first1=L.|last2=Marchenko|first2=S. V.|last3=Moffat|first3=A. F. J.|last4=Acker|first4=A.|year=2009|doi=10.1051/0004-6361/200912304|doi-access=free}}</ref>

<ref name=merrill>{{cite journal|bibcode=1925ApJ....61..389M|title=Discovery and Observations of Stars of Class Be|journal=Astrophysical Journal|volume=61|pages=389|last1=Merrill|first1=P. W.|last2=Humason|first2=M. L.|last3=Burwell|first3=C. G.|year=1925|doi=10.1086/142899|doi-access=free}}</ref>

<ref name=gcvs2>khi 2 Ori, database entry, [http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/iii.dat The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars] {{Webarchive|url=https://web.archive.org/web/20170620004609/http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/iii.dat |date=2017-06-20 }}, Sternberg Astronomical Institute, Moscow, Russia.  Accessed on line January 14, 2011.</ref>

<ref name=bsc1>[http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=V/50/catalog&recno=2135 HR 2135], database entry, The Bright Star Catalogue,  5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID [http://vizier.u-strasbg.fr/viz-bin/Cat?V/50 V/50].  Accessed on line January 14, 2011.</ref>

<ref name=baas25_1319>{{citation | last1=Garrison | first1=R. F. | title=Anchor Points for the MK System of Spectral Classification | journal=Bulletin of the American Astronomical Society | volume=25 | page=1319 | date=December 1993 | bibcode=1993AAS...183.1710G | url=http://www.astro.utoronto.ca/~garrison/mkstds.html | accessdate=2012-02-04 | archive-date=2019-06-25 | archive-url=https://web.archive.org/web/20190625094716/http://www.astro.utoronto.ca/~garrison/mkstds.html | url-status=dead }}</ref>
<!-- Unused citation
<ref name="Neuhauser">{{citation | last1=Tetzlaff | first1=N. | last2=Neuhäuser | first2=R. | last3=Hohle | first3=M. M. | title=A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun | journal=Monthly Notices of the Royal Astronomical Society | volume=410 | issue=1 | pages=190–200 |date=January 2011 | doi=10.1111/j.1365-2966.2010.17434.x | bibcode=2011MNRAS.410..190T |arxiv = 1007.4883 }}</ref>

<ref name="Underhill">{{citation | display-authors=1 | last1=Underhill | first1=A. B. | last2=Divan | first2=L. | last3=Prevot-Burnichon | first3=M.-L. | last4=Doazan | first4=V. | title=Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars | journal=Monthly Notices of the Royal Astronomical Society | volume=189 | pages=601–605 |date=November 1979 | bibcode=1979MNRAS.189..601U | doi=10.1093/mnras/189.3.601}}</ref>
-->

<ref name=rv>{{cite book |bibcode=1953GCRV..C......0W|title=General catalogue of stellar radial velocities|publisher=Carnegie Institution of Washington|last1=Wilson|first1=Ralph Elmer|year=1953}}</ref>

<ref name="Neuhauser">{{Cite journal | last1 = Tetzlaff | first1 = N. | last2 = Neuhäuser | first2 = R. | last3 = Hohle | first3 = M. M. | title = A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun | doi = 10.1111/j.1365-2966.2010.17434.x | journal = Monthly Notices of the Royal Astronomical Society | volume = 410 | pages = 190–200 | year = 2011 |arxiv = 1007.4883 |bibcode = 2011MNRAS.410..190T | s2cid = 118629873 }}</ref>

<ref name=crowther>{{Cite journal | last1 = Crowther | first1 = P. A. | last2 = Lennon | first2 = D. J. | last3 = Walborn | first3 = N. R. | title = Physical parameters and wind properties of galactic early B supergiants | doi = 10.1051/0004-6361:20053685 | journal = Astronomy and Astrophysics | volume = 446 | pages = 279–293 | year = 2006 |arxiv = astro-ph/0509436 |bibcode = 2006A&A...446..279C | s2cid = 18815761 }}</ref>

}}
{{Stars of Orion}}

{{DEFAULTSORT:Chi2 Orionis}}
[[Category:Orion (constellation)]]
[[Category:B-type supergiants]]
[[Category:Flamsteed objects|Orionis, 62]]
[[Category:Bayer objects|Orionis, Chi2]]
[[Category:Henry Draper Catalogue objects|041117]]
[[Category:Hipparcos objects|028716]]
[[Category:Alpha Cygni variables]]
[[Category:Bright Star Catalogue objects|2135]]
[[Category:Durchmusterung objects|BD+20 1233]]

{{Sourceattribution|Chi2 Orionis}}