Theta Centauri

{{Short description|Star in the constellation Centaurus}} {{Starbox begin}} {{Starbox image | image = {{Location mark | image=Centaurus IAU.svg | float=center | width=240 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=θ Cen | x%=35.0 | y%=35.5 }} | caption=Location of θ Centauri (circled) }} {{Starbox observe | epoch = J2000.0 | ra = {{RA|14|06|40.94752}}<ref name=aaa474_2_653/> | dec = {{DEC|-36|22|11.8371}}<ref name=aaa474_2_653/> | appmag_v = +2.06<ref name=clpl4_99/> | constell = [[Centaurus]] }} {{Starbox character | class = K0 III<ref name=aj132_1_161/> | b-v = +0.99<ref name=clpl4_99/> | u-b = +0.90<ref name=clpl4_99/> | variable = | type = [[Red clump]]<ref name=Fuhrmann2012/> }} {{Starbox astrometry | radial_v = +1.3<ref name=scfs/> | prop_mo_ra = −520.53<ref name=aaa474_2_653/> | prop_mo_dec = −518.06 | pm_footnote = <ref name=aaa474_2_653/> | parallax = 55.45 | p_error = 0.20 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = 0.87<ref name=aaa343_222/> }} {{Starbox detail | mass = {{Val|1.32|0.08}}<ref name=Rudrasingam2026/> | radius = {{val|10.96|0.20}}<ref name=Rudrasingam2026/> | luminosity = {{val|56.0|2.6|2.5}}<ref name=Fuhrmann2012/>{{efn|name=luminosity}} | temperature = {{val|4853|41|fmt=commas}}<ref name=ottoni/> | gravity = {{val|2.61|0.09}}<ref name=ottoni/> | metal_fe = {{val|−0.047|0.032}}<ref name=ottoni/> | rotational_velocity = }} {{Starbox catalog | names = {{odlist | name=Menkent | B=θ Cen, Theta Cen | F=5 Centauri | CD=−35° 9260 | FK5=520 | GJ=539 | HD=123139 | HIP=68933 | HR=5288 | LHS=2858 | SAO=205188 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = tet+Cen }} {{Starbox end}}

'''Theta Centauri''' is a single<ref name=Furhmann/> [[star]] in the southern [[constellation]] of [[Centaurus]], the [[centaur]]. It has the official name '''Menkent''', pronounced {{IPAc-en|'|m|E|N|k|E|n|t}};<ref name=Kunitzsch/><ref name="IAU-LSN"/> ''Theta Centauri'' is its [[Bayer designation]], which is [[Romanization of Greek|Latinized]] from '''θ Centauri''' and abbreviated Theta Cen or θ Cen. With an [[Apparent magnitude|apparent visual magnitude]] of +2.06,<ref name=clpl4_99/> it is the [[List of stars in Centaurus|fourth-brightest member of the constellation]]. Based on [[stellar parallax|parallax]] measurements obtained during the [[Hipparcos]] mission, it is about {{Convert|58.8|ly|pc|abbr=off|lk=on}} distant.<ref name=aaa474_2_653/> It has a relatively high [[proper motion]], traversing the [[celestial sphere]] at the rate of {{val|0.73|u=arcsecond/yr}}.<ref name=Bakos_et_al_2002/> This suggests that Menkent may have originated in the outer disk of the [[Milky Way]] and is merely passing through the solar neighborhood.<ref name="kaler" />

==Nomenclature==

''θ Centauri'', [[Latinisation of names|Latinised]] to ''Theta Centauri'', is the star's [[Bayer designation]].

It bore the traditional name of ''Menkent'' derived from the [[Arabic]] word مَنْكِب‎ (mankib) for "shoulder" (of the Centaur), apparently blended with a shortened form of "kentaurus" (centaur). In 2016, the [[International Astronomical Union]] organized a [[IAU Working Group on Star Names|Working Group on Star Names]] (WGSN)<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 | archive-date=10 June 2016 | archive-url=https://web.archive.org/web/20160610172014/https://www.iau.org/science/scientific_bodies/working_groups/280/ | url-status=dead }}</ref> to catalog and standardize proper names for stars. The WGSN approved the name ''Menkent'' for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.<ref name="IAU-LSN"/>

In [[Chinese astronomy|Chinese]], {{lang|zh|庫樓}} ({{lang|zh-Latn|Kù Lóu}}), meaning ''[[Horn (Chinese constellation)|arsenal]]'', refers to an [[asterism (astronomy)|asterism]] consisting of Theta Centauri, [[Zeta Centauri]], [[Eta Centauri]], [[2 Centauri]], [[HD 117440]], [[Xi1 Centauri|Xi¹ Centauri]], [[Gamma Centauri]], [[Tau Centauri]], [[D Centauri]] and [[Sigma Centauri]].<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, the [[Chinese star names|Chinese name]] for Theta Centauri itself is {{lang|zh|庫樓三}} ({{lang|zh-Latn|Kù Lóu sān}}, {{langx|en|the Third Star of Arsenal}}).<ref>{{in lang|zh}} [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_m.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive|url=https://web.archive.org/web/20110130063012/http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_m.htm |date=2011-01-30 }}, Hong Kong Space Museum. Accessed on line November 23, 2010.</ref>

== Properties ==

This is an [[stellar evolution|evolved]] [[giant star]] with a [[stellar classification]] of K0 III<ref name=aj132_1_161/> and 1.27 times the [[mass of the Sun]]. It is believed to be fusing helium into carbon and heavier elements within its core, qualifying it as a [[red clump]] star.<ref name=Fuhrmann2012/> It is a southern analog to [[Pollux (star)|Pollux]], the brightest star in [[Gemini (constellation)|Gemini]] and the closest giant to the Sun.<ref name="kaler" /> Menkent is 11 times larger than the Sun<ref name=Rudrasingam2026/> and 56 times more luminous.<ref name=Fuhrmann2012/> The [[stellar atmosphere|outer envelope]] has an [[effective temperature]] of 4,853 [[Kelvin|K]],<ref name=ottoni/> giving it the orange-hued glow of a cool, [[K-type star]].<ref name=csiro/> Soft X-ray emission has been detected from this star, which has an estimated X-ray luminosity of {{nowrap|1.4 × 1027 erg s−1}}.<ref name=aaa335_591/>

==See also== *[[List of nearest giant stars]]

==Notes== {{notelist|notes=

{{efn|name=luminosity|1=Calculated using [[absolute bolometric magnitude]] of +{{val|0.37|0.05}} via the equation 100.4(4.74−Mbol).}}

}}

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

<ref name=ottoni>{{Cite journal | display-authors=1 |last1=Ottoni |first1=G. |last2=Udry |first2=S. |last3=Ségransan |first3=D. |last4=Buldgen |first4=G. |last5=Lovis |first5=C. |last6=Eggenberger |first6=P. |last7=Pezzotti |first7=C. |last8=Adibekyan |first8=V. |last9=Marmier |first9=M. |last10=Mayor |first10=M. |last11=Santos |first11=N. C. |last12=Sousa |first12=S. G. |last13=Lagarde |first13=N. |last14=Charbonnel |first14=C. |date=2022-01-01 |title=CORALIE radial-velocity search for companions around evolved stars (CASCADES). I. Sample definition and first results: Three new planets orbiting giant stars |bibcode=2022A&A...657A..87O |journal=Astronomy and Astrophysics |volume=657 |pages=A87 |doi=10.1051/0004-6361/202040078 |issn=0004-6361|arxiv=2201.01528 }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/A+A/657/A87&HD=123139 Theta Centauri's database entry] at [[VizieR]].</ref>

<ref name=Rudrasingam2026> {{Cite journal | last1=Rudrasingam | first1=Jonatan | last2=Bedding | first2=Timothy R | last3=Pope | first3=Benjamin J S | last4=Pedersen | first4=May Gade | last5=Lund | first5=Mikkel N | last6=White | first6=Timothy R | last7=Hey | first7=Daniel | title=Halo photometry and asteroseismology for 98 of the brightest stars observed by 'TESS' | journal=[[Monthly Notices of the Royal Astronomical Society]] | publisher=[[Oxford University Press]] (OUP) | volume=547 | issue=4 | date=2026-02-28 | article-number=stag413 | arxiv=2602.22472 | bibcode=2026MNRAS.547ag413R | doi=10.1093/mnras/stag413 | doi-access=free | issn=0035-8711 }}</ref>

<ref name=Fuhrmann2012>{{cite journal | last1=Fuhrmann | first1=K. | last2=Chini | first2=R. | title=Multiplicity among F-type Stars | journal=The Astrophysical Journal Supplement | volume=203 | issue=2 | pages=20 | id=30 | date=2012 | doi=10.1088/0067-0049/203/2/30 | bibcode=2012ApJS..203...30F | doi-access=free }}</ref>

<ref name=aaa474_2_653>{{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>

<ref name=aj132_1_161>{{cite journal | display-authors=1 | last1=Gray | first1=R. O. | first2=C. J. | last2=Corbally | first3=R. F. | last3=Garrison | first4=M. T. | last4=McFadden | first5=P. E. | last5=Robinson | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 | s2cid=119476992 }}</ref>

<ref name=scfs>{{cite journal | display-authors=1 | title=Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions | journal=Veröff. Astron. Rechen-Inst. Heidelb | volume=35 | last1=Wielen | first1=R. | last2=Schwan | first2=H. | last3=Dettbarn | first3=C. | last4=Lenhardt | first4=H. | last5=Jahreiß | first5=H. | last6=Jährling | first6=R. | publisher=Astronomisches Rechen-Institut Heidelberg | issue=35 | date=1999 | page=1 | bibcode=1999VeARI..35....1W }}</ref>

<ref name=clpl4_99>{{cite journal | display-authors=1 | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | title=UBVRIJKL photometry of the bright stars | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | issue=99 | pages=99 | date=1966 | bibcode=1966CoLPL...4...99J }}</ref>

<ref name=aaa335_591>{{cite journal | display-authors=1 | last1=Schroeder | first1=K.-P. | last2=Huensch | first2=M. | last3=Schmitt | first3=J. H. M. M. | title=X-ray activity and evolutionary status of late-type giants | journal=Astronomy and Astrophysics | volume=335 | pages=591–595 |date=July 1998 | bibcode=1998A&A...335..591S }}</ref>

<ref name=SIMBAD>{{cite simbad | title=tet Cen | access-date=2012-03-01 }}</ref>

<ref name=csiro>{{cite web | title=The Colour of Stars | date=December 21, 2004 | work=Australia Telescope, Outreach and Education | publisher=Commonwealth Scientific and Industrial Research Organisation | url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | access-date=2012-01-16 | archive-date=2013-12-03 | archive-url=https://web.archive.org/web/20131203222826/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | url-status=dead }}</ref>

<ref name=kaler>{{cite web | first1=James B. | last1=Kaler | title=MENKENT (Theta Centauri) | work=Stars | publisher=University of Illinois | url=http://stars.astro.illinois.edu/sow/menkent.html | access-date=2012-03-01 }}</ref>

<ref name=aaa343_222>{{cite journal | display-authors=1 | last1=Elgarøy | first1=Øystein | last2=Engvold | first2=Oddbjørn | last3=Lund | first3=Niels | title=The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity | journal=Astronomy and Astrophysics | volume=343 | pages=222–228 |date=March 1999 | bibcode=1999A&A...343..222E }}</ref>

<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>

<ref name="IAU-LSN">{{cite web | title=Naming Stars | publisher=IAU.org | url=https://www.iau.org/public/themes/naming_stars/ | access-date=18 June 2018 | archive-date=10 March 2025 | archive-url=https://web.archive.org/web/20250310063743/https://www.iau.org/public/themes/naming_stars/ | url-status=dead }}</ref>

<ref name=Bakos_et_al_2002>{{cite journal | display-authors=1 | last1=Bakos | first1=Gáspár Á. | last2=Sahu | first2=Kailash C. | last3=Németh | first3=Péter | title=Revised Coordinates and Proper Motions of the Stars in the Luyten Half-Second Catalog | journal=The Astrophysical Journal Supplement Series | volume=141 | issue=1 | pages=187–193 | date=July 2002 | doi=10.1086/340115 | bibcode=2002ApJS..141..187B | arxiv=astro-ph/0202164 | s2cid=36667868 }}</ref>

<ref name=Furhmann>{{Cite journal | display-authors=1 | title=Multiplicity among Solar-type Stars | last1=Fuhrmann | first1=K. | last2=Chini | first2=R. | last3=Kaderhandt | first3=L. | last4=Chen | first4=Z. | journal=The Astrophysical Journal | language=en | volume=836 | issue=1 | pages=139 | date=February 2017 | doi=10.3847/1538-4357/836/1/139 | doi-access=free | bibcode=2017ApJ...836..139F | issn=0004-637X}}</ref>

}}

[[Category:K-type giants]] [[Category:Population I stars]]  [[Category:Centaurus]] [[Category:Bayer objects|Centauri, Theta]] [[Category:Bright Star Catalogue objects|5288]] [[Category:Durchmusterung objects|CD-35 09260]] [[Category:Flamsteed objects|Centauri, 5]] [[Category:Gliese and GJ objects|0539]] [[Category:Henry Draper Catalogue objects|123139]] [[Category:Hipparcos objects|068933]] [[Category:Stars with proper names|Menkent]] [[Category:Brightest stars]]