Editing Beta Centauri

{{Short description|Triple star system in the constellation Centaurus}}
{{For|other uses of the name "Hadar"|Hadar (disambiguation)}}
{{hatnote group|
{{about-distinguish|the star system β Centauri|HD 102964{{!}}B Centauri|HD 129116{{!}}b Centauri|Alpha Centauri B{{!}}α Centauri B}}
{{for|the exoplanet|b Centauri b}}
}}
{{Starbox begin
| name=β Centauri/Hadar
}}
{{Starbox image
 | image=
{{Location mark
|image=Centaurus constellation map.svg|float=center|width=280
|alt=|label=|position=right
|mark=Red circle.svg|mark_width=12|mark_link=Beta Centauri|x=421|y=845
}}
|caption=Location of β Centauri (circled)
}}
{{Starbox observe
| epoch    = J2000
| constell = [[Centaurus]]
| ra       = {{RA|14|03|49.40535}}<ref name=aaa474_2_653/>
| dec      = {{DEC|-60|22|22.9266}}<ref name=aaa474_2_653/>
| appmag_v = 0.61<ref name=hr/>
}}
{{Starbox character
| b-v      = −0.23<ref name=hr/>
| u-b      = −0.98<ref name=hr/>
}}
{{Starbox character|no_heading=y
| component = β Cen Aa
| class    = B1&nbsp;III<ref name=aaa455_1_259/>
| variable = [[Beta Cephei variable|β Cep]]/[[Slowly pulsating B-type star|SPB]]<ref name=Pigulski16/>
| component2 = β Cen Ab
| class2    = B1&nbsp;III<ref name=aaa455_1_259/>
| variable2 =
}}
{{Starbox character|no_heading=y
| component = β Cen B
| class    = B1V?<ref name=aaa455_1_259/>
}}
{{Starbox astrometry
| radial_v = {{val|+9.59|0.23|0.21}}<ref name=Pigulski16/>
| prop_mo_ra  = −33.27
| prop_mo_dec = −23.16
| pm_footnote = <ref name=aaa474_2_653/>
| parallax = 9.04
| p_error  = 0.04
| parallax_footnote = <ref name=Pigulski16/>
| dist_footnote = <ref name=Pigulski16/>
| absmag_v = {{val|−4.9|0.2}}<ref name=schultz2019/>
}}
{{Starbox orbit
| reference = <ref name=Pigulski16/>
| primary = β Cen Aa
| name = β Cen Ab
| period = {{val|0.97720|0.00004}}
| period_unitless = {{val|356.915|0.015|ul=days}}
| axis = {{val|0.02515|0.09|0.08}}
| axis_unitless =
| eccentricity = {{val|0.8245|0.006}}
| inclination = {{val|67.68|0.12}}
| node ={{val|108.80|0.14|0.15}}
| periastron = 2452000.15202
| periarg = {{val|60.87|0.26|0.25}}
| periarg_primary =
| k1 = 62.9
| k2 = 72.35
}}
{{Starbox orbit
| reference = <ref name=msc/>
| primary = β Cen A
| name = β Cen B
| period = 288.267
| period_unitless =
| axis = 0.870
| axis_unitless =
| eccentricity =
| inclination =
| node =
| periastron =
| periarg =
| periarg_primary =
| k1 =
| k2 =
}}
{{Starbox detail
| component1  = β Cen Aa
| radius      = {{solar radius calculator|type=AD|0.77|0.1106|decimals=2}}{{efn|name=radius|group=note}}
| mass        = {{val|12.02|0.13}}<ref name=Pigulski16/>
| luminosity  = {{val|31,600|18,500|11,700|fmt=commas}}<ref name=schultz2019/>
| temperature = {{val|25,000|2,000|fmt=commas}}<ref name=schultz2019/>
| gravity = {{val|3.55|0.11}}<ref name=schultz2019/>
| rotational_velocity = {{val|190|20}}<ref name=alecian2011/>
| age_myr = {{val|14.1|0.6}}<ref name=aaa455_1_259/>
| component2  = β Cen Ab
| radius2      = {{solar radius calculator|type=AD|0.72|0.1106|decimals=2}}{{efn|name=radius|group=note}}
| mass2        = {{val|10.58|0.18}}<ref name=Pigulski16/>
| luminosity2  = {{val|25,100|14,700|9,300|fmt=commas}}<ref name=schultz2019/>
| temperature2 = {{val|23,000|2,000|fmt=commas}}<ref name=schultz2019/>
| gravity2 = {{val|3.55|0.11}}<ref name=schultz2019/>
| rotational_velocity2 = {{val|75|15}}<ref name=alecian2011/>
| age_myr2 = {{val|14.1|0.6}}<ref name=aaa455_1_259/>
}}
{{Starbox detail|no_heading=y
| component1  = β Cen B
| radius      =
| mass        = 4.61<ref name=msc/>
| luminosity  =
| temperature =
| gravity =
| age_myr = {{val|14.1|0.6}}<ref name=aaa455_1_259/>
}}
{{Starbox catalog
| names = {{odlist | name=Agena | name2=Hadar<ref name=allen1963/> | HR=5267 | HD=122451 | CD=−59°5365 | LHS=51 | SAO=252582 | FK5=518 | HIP=68702 | GC=18971 | CCDM=J14038-6022 }}<ref name=SIMBAD/>
}}
{{Starbox reference
| Simbad=HD+122451
}}
{{Starbox end}}

'''Beta Centauri''' is a triple [[star system]] in the southern [[constellation]] of [[Centaurus]]. It is officially called '''Hadar''' ({{IPAc-en|'|h|ei|d|ɑr}}). The [[Bayer designation]] of Beta Centauri is [[Latinisation of names|Latinised]] from '''β Centauri''', and abbreviated '''Beta Cen''' or '''β Cen'''. The system's combined [[apparent visual magnitude]] of 0.61 makes it the second-brightest object in Centaurus and the [[list of brightest stars|eleventh brightest star]] in the [[night sky]]. According to [[dynamical parallax]] measurements, the distance to this system is about {{Convert|361|ly|pc|abbr=off|lk=on|0}}.

==Nomenclature==
''β Centauri'' (Latinised to ''Beta Centauri'') is the star system's [[Bayer designation]].

It bore the traditional names ''Hadar'' and ''Agena''. ''Hadar'' comes from the [[Arabic]] حضار (the root's meaning is "to be present" or "on the ground" or "settled, civilized area"<ref name=wehr/>), while the name ''Agena'' {{IPAc-en|@|'|dZ|iː|n|@}} is thought to be derived from the [[Latin]] ''genua'', meaning "knees", from the star's position on the left knee of the [[centaur]] depicted in the constellation [[Centaurus]]. In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. The WGSN approved the name ''Hadar'' for the star β Centauri Aa on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/> 

The Chinese name for the star is 马腹一 ([[Standard Chinese|Mandarin]]: mǎ fù yī, "the First Star of the Horse's Abdomen").<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060729.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日] {{Webarchive|url=https://web.archive.org/web/20110522124325/http://aeea.nmns.edu.tw/2006/0607/ap060729.html |date=2011-05-22 }}</ref>

The [[Wergaia|Boorong]] people indigenous to what is now northwestern [[Victoria, Australia]] named it ''Bermbermgle'' (together with [[α Centauri]]),<ref name=hamacher/> two brothers who were noted for their courage and destructiveness, and who spear and kill Tchingal, "The Emu" ([[Coalsack Nebula]]).<ref name=stanbridge/> The [[Wotjobaluk people]] name the two brothers ''Bram-bram-bult''.<ref name=hamacher/>

==Visibility==
Beta Centauri is one of the [[list of brightest stars|brightest stars]] in the sky at [[apparent magnitude|magnitude]] 0.61. Its brightness varies by a few hundredths of a magnitude, too small to be noticeable to the naked eye.<ref name=lefevre2009/> Because of its spectral type and the detection of pulsations, the Aa component has been classified as a [[β Cephei variable]].<ref name=gcvs/>

Beta Centauri is well known in the [[Southern Hemisphere]] as the inner of the two "Pointers" to the constellation [[Crux]], popularly known as the Southern Cross. A line made from the other pointer, [[Alpha Centauri]], through Beta Centauri leads to within a few degrees of [[Gacrux]], the star at the north end of the cross. Using Gacrux, a navigator can draw a line with [[Acrux]] at the south end to effectively determine south.<ref name=kysela_lanterman1976/>

==Stellar system==
The Beta Centauri system is made up of three [[star]]s: Beta Centauri Aa, Beta Centauri Ab, and Beta Centauri B. All the spectral lines detected are consistent with a B1-type star, with only the line profiles varying, so it is thought that all three stars have the same spectral type.

In 1935, [[Joan Voûte]] identified Beta Centauri B, giving it the identifier VOU 31. The companion is separated from the primary by 1.3 [[seconds of arc]], and has remained so since the discovery, although the position angle has changed six degrees since. Beta Centauri B is a B1 dwarf with an apparent magnitude of 4.

In 1967, Beta Centauri's observed variation in [[radial velocity]] suggested that Beta Centauri A is a [[binary star]].<ref>{{cite journal | last = Breger | first = M. | title = A Spectroscopic Study of Two Southern B-Type Variables | date = May 1967| journal = Monthly Notices of the Royal Astronomical Society | volume = 136 | issue = 1 | pages = 51–59 | doi = 10.1093/mnras/136.1.51| doi-access =  free}}</ref><ref name=Robertson/> This was confirmed in 1999.<ref name=Robertson>{{cite journal | last1 = Robertson | first1 = J.G. | last2= Bedding | first2=T.G. | last3= Aerts | first3= C.| last4= Waelkens | first4= C. | last5= Marson | first5= R.G. | last6= Barton | first6= J.R. | title = Interferometry and spectroscopy of β Cen: a β Cephei star in a binary system| date = January 1999| journal = Monthly Notices of the Royal Astronomical Society | volume = 302 | issue = 1 | pages = 245–252 | doi =10.1046/j.1365-8711.1999.02068.x| arxiv = astro-ph/9809158 | bibcode = 1999MNRAS.302..245R | doi-access= free }}</ref> It consists of a pair of stars, β Centauri Aa and β Centauri Ab, of similar mass that orbit each other over a period of 357&nbsp;days with a large [[Orbital eccentricity|eccentricity]] of about 0.8245.<ref name=Pigulski16/>

The pair were calculated to be separated by a mean distance of roughly 4&nbsp;[[astronomical unit]]s (based on a distance to the system of 161 parsecs) in 2005.<ref name=aaa437_2_599/>

[[File:BetCenLightCurve.png|thumb|left|A [[light curve]] for Beta Centauri, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]] data.<ref name=MAST/>]]
Both Aa and Ab apparently have a [[stellar classification]] of B1&nbsp;III,<ref name=aaa437_2_599/> with the [[luminosity class]] of III indicating [[giant star]]s that are [[stellar evolution|evolving]] away from the [[main sequence]]. Component Aa rotates much more rapidly than Ab, causing its spectral lines to be broader, and so the two components can be distinguished in the [[stellar spectrum|spectrum]]. Component Ab, the slow-rotating star, has a strong magnetic field although no detected [[chemically peculiar star|abundance peculiarities]] in its spectrum. Multiple pulsations modes have been detected in component Aa, some of which correspond to brightness variations, so this star is considered to be variable. The detected pulsation modes correspond to those for both [[β Cephei variable]]s and [[slowly pulsating B star]]s. Similar pulsations have not been detected in component Ab, but it is possible that it is also a variable star.<ref name=Pigulski16/>

Aa is 12.02 times as massive as the Sun, while Ab is 10.58 times as massive.<ref name=Pigulski16/> Their [[angular diameter]]s are estimated at 0.77 and 0.72 [[milliarcsecond]]s.<ref name=Davis2006/> At the system's distance of {{val|110.6|0.5|ul=parsec}}, this derive liner radii of {{solar radius calculator|type=AD|0.77|0.1106|decimals=1}} and {{solar radius calculator|type=AD|0.72|0.1106|decimals=1}} [[solar radii]], respectively.{{efn|name=radius|group=note}}

==Notes==
{{Notelist|group=note|notes=

{{Efn|name=radius|group=note|1=Radius calculated using [[angular diameter]]s (0.77 and 0.72 [[milliarcsecond]]s) and a [[parallax]] of 9.04 [[milliarcsecond]]s via the equation ''R''/{{Solar radius}} = (107.5{{*}}{{theta}})/{{pi}}, where {{theta}} is the angular diameter and {{pi}} is the parallax.<br>Sources:<br>Angular diameters{{emdash}}[[doi:10.1111/j.1365-2966.2004.08571.x|J Davis et al. (2006)]]<br>Parallax{{emdash}}[[arxiv:1602.02806|Pigulski et al. 2016]]}}

}}

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

<ref name=aaa474_2_653>{{cite journal |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>

<ref name=kysela_lanterman1976>{{cite book | first1=Will | last1=Kyselka | first2=Ray E. | last2=Lanterman | title=North Star to Southern Cross | location=Honolulu | publisher=[[University of Hawaii Press]] | year=1976 | isbn=0-8248-0419-8 | page=59 | url=https://books.google.com/books?id=H5dasxVgjSAC&pg=PA59 | bibcode=1976nsts.book.....K }}</ref>

<ref name=aaa437_2_599>{{cite journal | last1=Raassen | first1=A. J. J. | last2=Cassinelli | first2=J. P. | last3=Miller | first3=N. A. | last4=Mewe | first4=R. | last5=Tepedelenlioǧlu | first5=E. | title=XMM-Newton observations of β Centauri (B1 III): The temperature structure in the hot plasma and the photosphere-wind connection | journal=Astronomy and Astrophysics | volume=437 | issue=2 | pages=599–609 |date=July 2006 | doi=10.1051/0004-6361:20052650 | bibcode=2005A&A...437..599R | url=http://www.aanda.org/articles/aa/pdf/2005/26/aa2650-05.pdf | doi-access=free }}</ref>

<ref name=SIMBAD>{{cite web | title=V* bet Cen -- Variable Star of beta Cep type | work=SIMBAD | publisher=[[Centre de Données astronomiques de Strasbourg]] | url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Beta+Centauri | access-date=2011-12-19 }}</ref>

<ref name=allen1963>{{cite book | last=Allen | first=R. H. | year=1963 | author-link=Richard Hinckley Allen | title=Star Names: Their Lore and Meaning | url=https://archive.org/details/starnamestheirlo00alle/page/154 | access-date=2010-12-12 | edition=Reprint | publisher=Dover Publications Inc | location=New York | isbn=0-486-21079-0 | page=[https://archive.org/details/starnamestheirlo00alle/page/154 154] | url-access=registration }}</ref>

<ref name=Davis2006>{{Cite journal |last1=Davis |first1=J. |last2=Mendez |first2=A. |last3=Seneta |first3=E. B. |last4=Tango |first4=W. J. |last5=Booth |first5=A. J. |last6=O'Byrne |first6=J. W. |last7=Thorvaldson |first7=E. D. |last8=Ausseloos |first8=M. |last9=Aerts |first9=C. |last10=Uytterhoeven |first10=K. |date=2005-02-01 |title=Orbital parameters, masses and distance to β Centauri determined with the Sydney University Stellar Interferometer and high-resolution spectroscopy  |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=356 |issue=4 |pages=1362–1370 |doi=10.1111/j.1365-2966.2004.08571.x |doi-access=free |arxiv=astro-ph/0411054 |bibcode=2005MNRAS.356.1362D |issn=0035-8711|hdl=2066/32820 |hdl-access=free }}</ref>


<ref name=MAST>{{cite web
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 | publisher=Space Telescope Science Institute | access-date=29 September 2024}}</ref>

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<ref name=Pigulski16>{{cite journal | last1=Pigulski |first1=A. |last2=Cugier| first2=H. |last3=Popowicz| first3=A.| last4=Kuschnig| first4=R.| last5=Moffat| first5=A. F. J.| last6=Rucinski| first6=S. M.| last7=Schwarzenberg-Czerny| first7=A.| last8=Weiss| first8=W. W.| last9=Handler| first9=G.| last10=Wade| first10=G. A.| last11=Koudelka| first11=O.| last12=Matthews| first12=J. M.| last13=Mochnacki| first13=St.| last14=Orleański| first14=P.| last15=Pablo| first15=H.| last16=Ramiaramanantsoa| first16=T.| last17=Whittaker| first17=G.| last18=Zocłońska| first18=E.| last19=Zwintz| first19=K. | title=Massive pulsating stars observed by BRITE-Constellation. I. The triple system β Centauri (Agena) | journal=Astronomy and Astrophysics | volume=588 | id=A55 | pages=17|date=2016 | doi=10.1051/0004-6361/201527872 | bibcode=2016A&A...588A..55P|arxiv = 1602.02806 |s2cid=53382272 }}</ref>

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<ref name=msc>{{cite journal|title=MSC - a catalogue of physical multiple stars|last1=Tokovinin|first1=A. A.|journal=[[Astronomy & Astrophysics Supplement Series]]|volume=124|page=75|date=1997|bibcode=1997A&AS..124...75T|doi=10.1051/aas:1997181|doi-access=free}}</ref>

<ref name="IAU-CSN">{{cite web | url=https://www.iau.org/public/themes/naming_stars/#table | title=IAU Catalog of Star Names |access-date=12 August 2018}}</ref>

<ref name="WGSN">{{cite web |url=https://www.iau.org/science/scientific_bodies/working_groups/280/ |title=IAU Working Group on Star Names (WGSN) |access-date=22 May 2016}}</ref>

<ref name=wehr>{{cite book|author=Hans Wehr|title=A Dictionary of Modern Written Arabic|url=https://books.google.com/books?id=WTak55pG-_IC|year=1979|publisher=Otto Harrassowitz Verlag|isbn=978-3-447-02002-2}}</ref>

<ref name=hamacher>{{cite journal |last1=Hamacher |first1=Duane W. |last2=Frew |first2=David J. |year=2010 |title=An Aboriginal Australian Record of the Great Eruption of Eta Carinae |journal=Journal of Astronomical History & Heritage |volume=13 |issue=3 |pages=220–34 |doi=10.3724/SP.J.1440-2807.2010.03.06 |bibcode=2010JAHH...13..220H |arxiv=1010.4610|s2cid=118454721 }}</ref>

<ref name=stanbridge>{{cite journal |url=http://www.atnf.csiro.au/research/AboriginalAstronomy/literature/Stanbridge1857.pdf |last1=Stanbridge |first1=WM |year=1857 |title=On the Astronomy and Mythology of the Aboriginies of Victoria |journal=Transactions Philosophical Institute Victoria |volume=2 |pages=137–140 |archive-url=https://web.archive.org/web/20130602055546/http://www.atnf.csiro.au/research/AboriginalAstronomy/literature/Stanbridge1857.pdf |archive-date=2 June 2013 |url-status=dead }}</ref>

<ref name=schultz2019>{{cite journal |bibcode=2019MNRAS.485.1508S |title=The magnetic early B-type Stars II: Stellar atmospheric parameters in the era of Gaia |last1=Shultz |first1=M. E. |last2=Wade |first2=G. A. |last3=Rivinius |first3=Th |last4=Alecian |first4=E. |last5=Neiner |first5=C. |last6=Petit |first6=V. |last7=Wisniewski |first7=J. P. |author8=MiMeS Collaboration |author9=BinaMIcS Collaboration |journal=Monthly Notices of the Royal Astronomical Society |year=2019 |volume=485 |issue=2 |page=1508 |doi=10.1093/mnras/stz416 |doi-access=free |arxiv=1902.02713 |s2cid=119463660 }}</ref>

<ref name=alecian2011>{{cite journal |doi=10.1051/0004-6361/201118354 |title=First HARPSpol discoveries of magnetic fields in massive stars |year=2011 |last1=Alecian |first1=E. |last2=Kochukhov |first2=O. |last3=Neiner |first3=C. |last4=Wade |first4=G. A. |last5=De Batz |first5=B. |last6=Henrichs |first6=H. |last7=Grunhut |first7=J. H. |last8=Bouret |first8=J.-C. |last9=Briquet |first9=M. |last10=Gagne |first10=M. |last11=Naze |first11=Y. |last12=Oksala |first12=M. E. |last13=Rivinius |first13=T. |last14=Townsend |first14=R. H. D. |last15=Walborn |first15=N. R. |last16=Weiss |first16=W. |author17=Mimes Collaboration |journal=Astronomy & Astrophysics |volume=536 |pages=L6 |arxiv=1111.3433 |bibcode=2011A&A...536L...6A |s2cid=51173988 }}</ref>

<ref name=lefevre2009>{{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=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=B/gcvs|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>

}}

{{Sky|14|03|49.4|-|60|22|23|350}}
{{Stars of Centaurus}}
{{Portal bar|Astronomy|Stars|Outer space}}

{{DEFAULTSORT:Beta Centauri}}
<!-- Properties -->
[[Category:Beta Cephei variables]]
[[Category:B-type giants]]
[[Category:Spectroscopic binaries]]
[[Category:Triple star systems]]
<!-- Location/catalogues -->
[[Category:Centaurus]]
[[Category:Bayer objects|Centauri, Beta]]
[[Category:Bright Star Catalogue objects|5267]]
[[Category:Durchmusterung objects]]
[[Category:Henry Draper Catalogue objects|122451]]
[[Category:Hipparcos objects|068702]]
[[Category:Stars with proper names|Hadar]]