{{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=ζ Cen | x%=38.4 | y%=50.4 }} | caption=Location of ζ Centauri (circled) }} {{Starbox observe | epoch = J2000.0 | ra = {{RA|13|55|32.38565}}<ref name=aaa474_2_653/> | dec = {{DEC|−47|17|18.1482}}<ref name=aaa474_2_653/> | appmag_v = +2.55<ref name=clpl4_99/> | constell = [[Centaurus]] }} {{Starbox character | class = B2.5 IV<ref name=mnras410_1_190/> | b-v = −0.22<ref name=clpl4_99/> | u-b = −0.91<ref name=clpl4_99/> | variable = }} {{Starbox astrometry | radial_v = +6.5<ref name=gcsrv/> | prop_mo_ra = −57.37<ref name=aaa474_2_653/> | prop_mo_dec = −44.55<ref name=aaa474_2_653/> | parallax = 8.54 | p_error = 0.13 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = −2.79<ref name=Anderson2012/> }} {{Starbox orbit | reference = <ref name=hcoc233/> | period_unitless = 8.024 days | axis_unitless = 0.0014[[Arcsecond|"]]<ref name=aas44_47/> | eccentricity = 0.5 | periastron = 2413719.321 [[Julian day|JD]] | periarg = 290 }} {{Starbox detail | mass = {{val|7.8|0.1}}<ref name=mnras410_1_190/> | radius = {{val|5.80|0.53}}<ref name=aj129_3_1642/> | gravity = {{val|3.84|0.08}}<ref name=aj129_3_1642/> | metal_fe = | age_myr = {{val|39.8|5.7}}<ref name=mnras410_1_190/> | luminosity = 5,884<ref name=Anderson2012/> | temperature = {{val|23,561|283}}<ref name=aj129_3_1642/> | rotational_velocity = 235<ref name=csrv1970/> }} {{Starbox catalog | names = {{odlist | name=Leepwal | B=ζ Cen | CD=−46 8949 | CP=−46 6560 | HD=121263 | HIP=68002 | HR=5231 | SAO=224538 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=HD+121263 }} {{Starbox end}}
'''Zeta Centauri''' is a [[binary star]] system in the southern [[constellation]] of [[Centaurus]]. It has the proper name '''Leepwal''';<ref name="IAU-CSN-new"/> ''Zeta Centauri'' is its [[Bayer designation]]. With a combined [[apparent visual magnitude]] of +2.55,<ref name=clpl4_99/> it is one of the [[List of stars in Centaurus|brighter members]] of the constellation. This system is close enough to the Earth that its distance can be measured directly using the [[stellar parallax|parallax]] technique. This yields a value of roughly {{Convert|382|ly|pc|abbr=off|lk=on}}, with a 1.6% [[margin of error]].<ref name=aaa474_2_653/> It is drifting further away with a [[radial velocity]] of +6.5 km/s.<ref name=gcsrv/>
ζ Cen is a double-lined [[spectroscopic binary]] system,<ref name=aaa446_3_1071/> which indicates that the orbital motion was detected by shifts in the [[absorption line]]s of their combined spectra caused by the [[Doppler effect]]. The two stars orbit each other over a period of slightly more than eight days with an [[orbital eccentricity]] of about 0.5.<ref name=hcoc233/> The estimated [[angular separation]] of the pair is 1.4 [[milliarcsecond|mas]].<ref name=aas44_47/>
At an estimated age of 40 million years,<ref name=mnras410_1_190/> the primary component of this system appears to be in the [[subgiant star|subgiant]] stage of its [[stellar evolution|evolution]] with a [[stellar classification]] of B2.5 IV.<ref name=mnras410_1_190/> It is a large star with nearly 8<ref name=mnras410_1_190/> times the mass of the Sun and close to 6<ref name=aj129_3_1642/> times the Sun's radius. This star is rotating rapidly with a [[projected rotational velocity]] of {{nowrap|235 km s<sup>−1</sup>}}.<ref name=csrv1970/>
==Nomenclature== Zeta Centauri, [[Latinisation of names|Latinized]] from ζ Centauri, is the star's [[Bayer designation]]. Along with other modern Bayer designations in Centaurus, it was assigned by [[Nicolas Louis de Lacaille]] in his 1756 star catalog; the star referred to as ζ Centauri in Bayer's ''[[Uranometria]]'' of 1603 is [[Acrux]] in the [[Southern Cross]], then considered part of Centaurus.<ref name=Ridpath/>
This star has been referred to by the proper name Alnair {{IPAc-en|æ|'|n|ɛər}}, from {{langx|ar|نير بطن قنطورس|nayyir baṭan qanṭūris|lit=the bright (star) of the body of the [[Centaurus|centaur]]}},<ref name=kunitzsch_smart2006/><ref>''ibid''., p.28.</ref> though this was originally a name for [[Acrux]] (see above).<ref name=allen1899/><ref name=Ridpath/> Alnair is also the proper name of [[Alpha Gruis|α Gruis]] and was officially approved by the IAU as the name of that star.<ref name="IAU-CSN-new"/> This star has also been referred to as ''Baten Kentaurus'', from the same Arabic source.<ref name=rhoads1971/>
In [[Chinese astronomy|Chinese]], {{lang|zh|庫樓}} ({{lang|zh-Latn|Kù Lóu}}), meaning ''[[Horn (Chinese constellation)|Arsenal]]'', refers to an asterism consisting of ζ Centauri, [[Eta Centauri|η Centauri]], [[Theta Centauri|θ Centauri]], [[2 Centauri]], [[HD 117440]], [[Xi¹ Centauri|ξ<sup>1</sup> Centauri]], [[Gamma Centauri|γ Centauri]], [[Tau Centauri|τ Centauri]], [[D Centauri]] and [[Sigma Centauri|σ 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 ζ Centauri itself is {{lang|zh|庫樓一}} ({{lang|zh-Latn|Kù Lóu yī}}, {{langx|en|the First Star of Arsenal}}.)<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0607/ap060725.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 25 日] {{Webarchive|url=https://web.archive.org/web/20110522124501/http://aeea.nmns.edu.tw/2006/0607/ap060725.html |date=2011-05-22 }}</ref> (See also [[Iota Centauri|ι Centauri]].)
In [[Marshallese language|Marshallese]], this star is named Ļeepwal (pronounced leyepwal), the third of the ten sons of Lōktañūr ([[Capella]]).<ref name="ASE"/> The [[IAU Working Group on Star Names]] approved the name Leepwal for Zeta Centauri A on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN-new"/>
==References== {{Reflist|refs=
<ref name=aaa474_2_653>{{citation | 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=Anderson2012>{{cite XHIP | 66657 | mode=cs2 | access-date=2025-12-09 | postscript=. }}</ref>
<ref name=aj129_3_1642>{{citation | last1=Fitzpatrick | first1=E. L. | last2=Massa | first2=D. | title=Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry | journal=The Astronomical Journal | volume=129 | issue=3 | pages=1642–1662 |date=March 2005 | doi=10.1086/427855 | bibcode=2005AJ....129.1642F |arxiv = astro-ph/0412542 | s2cid=119512018 }}</ref>
<ref name=mnras410_1_190>{{citation | display-authors=1 | 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 | doi-access=free | bibcode=2011MNRAS.410..190T |arxiv = 1007.4883 | s2cid=118629873 }}</ref>
<ref name=gcsrv>{{citation | last=Wilson | first=R. E. | date=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institute of Washington D.C. | bibcode=1953GCRV..C......0W }}</ref>
<ref name=csrv1970>{{citation | last1=Bernacca | first1=P. L. | last2=Perinotto | first2=M. | title=A catalogue of stellar rotational velocities | journal=Contributi Osservatorio Astronomico di Padova in Asiago | volume=239 | issue=1 | date=1970 | page=1 | bibcode=1970CoAsi.239....1B }}</ref>
<ref name=clpl4_99>{{citation | 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 | date=1966 | page=99 | bibcode=1966CoLPL...4...99J }}</ref>
<ref name=SIMBAD>{{cite simbad | title=* zet Cen | mode=cs2 | postscript=. | access-date=2012-03-01 }}</ref>
<ref name=kunitzsch_smart2006>{{citation | last1=Kunitzsch | first1=P. | last2=Smart | first2=T. | date = 2006 | title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations | edition = 2nd revised | publisher = [[New Track Media#Sky Publishing|Sky Pub]] | location = [[Cambridge, Massachusetts|Cambridge]], [[Massachusetts|MA]] | isbn=978-1-931559-44-7 | page=4 }}</ref>
<ref name=aaa446_3_1071>{{citation | display-authors=1 | last1=van Rensbergen | first1=W. | last2=De Loore | first2=C. | last3=Jansen | first3=K. | title=Evolution of interacting binaries with a B type primary at birth | journal=Astronomy and Astrophysics | volume=446 | issue=3 | pages=1071–1079 |date=February 2006 | doi=10.1051/0004-6361:20053543 | bibcode=2006A&A...446.1071V | doi-access=free }}</ref>
<ref name=hcoc233>{{citation | first1=A. C. | last1=Maury | date=1922 | title=The Orbit of the Spectroscopic Binary ζ Centauri | journal=Harvard College Observatory Circular | volume=233 | pages=1–4 | bibcode=1922HarCi.233....1M }}</ref>
<ref name=aas44_47>{{citation | last1=Halbwachs | first1=J. L. | title=List of Estimated Angular Separations of Spectroscopic Binaries | journal=Astronomy and Astrophysics Supplement | volume=44 | page=47 |date=April 1981 | bibcode=1981A&AS...44...47H }}</ref>
<ref name=allen1899>{{citation | first1=R.H. | last1=Allen | title=Star Names: Their Lore and Meaning | date=1899 | url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Centaurus*.html | page=154 }}</ref>
<ref name=rhoads1971>{{citation | first=Jack W. | last=Rhoads | title=Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars | publisher=Jet Propulsion Laboratory, California Institute of Technology | url=https://ntrs.nasa.gov/api/citations/19720005197/downloads/19720005197.pdf | date=November 15, 1971 | postscript=. }}</ref>
<ref name="IAU-CSN-new">{{citation | postscript=. |title=IAU Catalog of Star Names |url=https://exopla.net/star-names/modern-iau-star-names/ |access-date=22 February 2025}}</ref>
<ref name="ASE">{{citation | postscript=. |title=Leepwal |url=https://ase.exopla.net/index.php/Leepwal |website=All Skies Encyclopaedia |publisher=[[IAU Working Group on Star Names]] |access-date=12 May 2025}}</ref>
<ref name=Ridpath>{{citation | postscript=. |last=Ridpath |first=Ian |author-link=Ian Ridpath |title=Star Tales - Crux |url=http://ianridpath.com/startales/crux.html |access-date=26 July 2025}}</ref>
}}
{{Stars of Centaurus}}
{{DEFAULTSORT:Zeta Centauri}} <!-- Physical properties --> [[Category:B-type subgiants]] [[Category:Spectroscopic binaries]] <!-- Constellation & catalogues --> [[Category:Centaurus]] [[Category:Bayer objects|Centauri, Zeta]] [[Category:Bright Star Catalogue objects|5231]] [[Category:Durchmusterung objects|CD-46 08949]] [[Category:Henry Draper Catalogue objects|121263]] [[Category:Hipparcos objects|068002]] [[Category:Stars with proper names|Leepwal]]