{{Short description|Star in the constellation Centaurus}} {{Starbox begin | name = δ Centauri }} {{Starbox image | image = {{Location mark | image=Centaurus IAU.svg | float=center | width=240 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=δ Cen | x%=60.0 | y%=54.2 }} | caption = Location of δ Centauri (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|12|08|21.49764}}<ref name=aaa474_2_653/> | dec = {{DEC|−50|43|20.7386}}<ref name=aaa474_2_653/> | appmag_v = +2.57<ref name=aj84_1713/> {{nowrap|(2.51 - 2.65<ref name=gcvs/>)}} | constell = [[Centaurus]]<ref name=Anderson2012/> }} {{Starbox character | type = | class = B2Vne<ref name=levenhagen/> or B2 IVne<ref name=houk1979/> | b-v = −0.13<ref name=aj84_1713/> | u-b = −0.92<ref name=aj84_1713/> | variable = [[Gamma Cassiopeiae variable|γ Cas]]<ref name=gcvs/> }} {{Starbox astrometry | radial_v = +11<ref name=rgcrv/> | prop_mo_ra = −49.94< | prop_mo_dec = −7.19 | pm_footnote = <ref name=aaa474_2_653/> | parallax = 7.86 | p_error = 0.47 | parallax_footnote = <ref name=aaa474_2_653/> | absmag_v = −2.94<ref name=Anderson2012/> }} {{Starbox detail | age_myr = {{val|21.5|1.5}}<ref name=mnras410_1_190/> | metal_fe = | gravity = {{val|3.43|0.03}}<ref name=arcos/> | mass = {{val|8.7|0.3}}<ref name=levenhagen/> | radius = {{val|8.18|0.16}}<ref name=arcos/> | rotational_velocity = {{val|263|14}}<ref name=fremat/> | rotation = | luminosity = 5,129<ref name=levenhagen/> | temperature = {{val|22230|650|fmt=commas}}<ref name=levenhagen/> }} {{Starbox catalog | names = {{odlist | B=δ Cen | CD=−50°6697 | CPD=−50°4862 | FK5=452 | HD=105435 | HIP=59196 | HR=4621 | SAO=239689 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = Delta+Cen }} {{Starbox end}}
'''Delta Centauri''' is a [[star]] in the southern [[constellation]] of [[Centaurus]]. Its name is a [[Bayer designation]] that is [[Romanization of Greek|Latinized]] from δ Centauri, and abbreviated Delta Cen or δ Cen. The [[apparent visual magnitude]] of this star is +2.57,<ref name=aj84_1713/> making it readily visible to the [[naked eye]]. Based upon [[stellar parallax|parallax]] measurements, it is located at a distance of about {{Convert|410|ly|pc|abbr=off|lk=on}} from the [[Earth]].<ref name=aaa474_2_653/> The star is drifting further away with a [[radial velocity]] of +11 km/s.<ref name=rgcrv/>
==Properties== [[File:DeltaCenLightCurve.png|thumb|left|A [[light curve]] for Delta Centauri, plotted from ''[[Hipparcos]]'' data<ref name=HipDataAccess/>]] δ Centauri is a [[shell star]], with a distinctive [[stellar spectrum|spectrum]] created by material thrown off into a disk by its rapid rotation. It is also a [[variable star]] whose brightness varies from magnitude +2.51 to +2.65. It has been classified as a [[Gamma Cassiopeiae variable|γ Cassiopeiae type]] variable.<ref name=aaa488_3_L67/> The energy from this star is being radiated at an [[effective temperature]] of over 22,000 K from the outer envelope, giving it the blue-white hue of a [[B-type star]].<ref name=csiro/> It has a radius of 6.5 times the [[solar radius|radius of the Sun]]<ref name=aaa505_2_687/> and 8.7 times the [[solar mass|Sun's mass]].<ref name=aaa505_2_687/>
The [[stellar classification]] of this star is B2Vne,<ref name=levenhagen/> which presents as a [[B-type main-sequence star]]. [[Nancy Houk|N. Houk]] in 1979 found a class of B2IVne,<ref name=houk1979/> with the [[luminosity class]] of IV suggesting that this may be a [[subgiant star]] that has exhausted the hydrogen at its core and begun to [[stellar evolution|evolve]] away from the [[main sequence]]. Detailed study of the spectrum suggests that the disparity is due to [[gravity darkening]] which makes the subgiant spectrum appear similar to a main-sequence star.<ref name=meilland2009/> The star is spinning rapidly, with the resulting [[Doppler effect]] giving its spectrum broad [[absorption line]]s as indicated by the 'n'. The suffix 'e' means this is a classical [[Be star]], which is a type of hot star that has not yet evolved into a [[supergiant star|supergiant]] and is surrounded by circumstellar gas. The presence of this gas creates an [[infrared excess|excess emission of infrared]], along with [[emission line]]s in the star's spectrum. Most of it is concentrated around the equator, forming a disk.<ref name=aaa505_2_687/>
Some of the variation in this star may be explained by assuming it is a [[binary star]] system. This proposed secondary star would need to have about 4–7 times the Sun's mass and be orbiting with a period of at least 4.6 years at a minimum separation of 6.9 [[Astronomical Unit]]s.<ref name=aaa488_3_L67/> δ Centauri shares a [[common proper motion]] with the nearby stars [[HD 105382]] and HD 105383, so they may form a small cluster or perhaps a triple star system.<ref name=aaa488_3_L67/> It is a [[proper motion]] member of the Lower Centaurus–Crux sub-group in the [[Scorpius–Centaurus association|Scorpius–Centaurus]] [[Stellar association|OB association]], the nearest such of association of co-moving massive stars to the Sun.<ref name=aaa216_1_44/>
==Etymology== In [[Chinese language|Chinese]], {{lang|zh|馬尾}} ({{lang|zh-Latn|Mǎ Wěi}}), meaning ''[[Chinese constellations#The Southern Asterisms (近南極星區)|Horse's Tail]]'', refers to an asterism consisting of δ Centauri, [[G Centauri]] and [[Rho Centauri|ρ Centauri]].<ref name=zh/> Consequently, δ Centauri itself is known as {{lang|zh|馬尾三}} ({{lang|zh-Latn|Mǎ Wěi sān}}, {{langx|en|the Third Star of Horse's Tail}}.).<ref name=AEEA/> From this Chinese name, the name '''Ma Wei''' appeared.<ref name=Allen/>
The people of [[Aranda people|Aranda]] and [[Luritja]] tribe around [[Hermannsburg]], [[Central Australia]], named '''Iritjinga''', "The Eagle-hawk", a quadrangular arrangement comprising this star, [[Gamma Centauri|γ Cen]] (Muhlifain), [[Gamma Crucis|γ Cru]] (Gacrux), and [[Delta Crucis|δ Cru]] (Imai).<ref name=Haynes/>
==See also== * [[Traditional Chinese star names#Centaurus|Traditional Chinese star names]]
==References== {{Reflist|30em|refs=
<ref name=SIMBAD>{{cite simbad | title=Del Cen | access-date=2025-12-08 | postscript=. | mode = cs2 }}</ref>
<ref name=Haynes>{{citation | postscript=. | display-authors=1 | first1=Raymond | last1=Haynes | first2=Roslynn D. | last2=Haynes | first3=David | last3=Malin| first4=Richard | last4=McGee | title=Explorers of the Southern Sky: A History of Australian Astronomy|url=https://books.google.com/books?id=XoeiJxMmXZ8C|year=1996|publisher=Cambridge University Press|isbn=978-0-521-36575-8|page=8}}</ref>
<ref name=arcos>{{citation | postscript=. | display-authors=1 |last1=Arcos |first1=C |last2=Kanaan |first2=S |last3=Chávez |first3=J |last4=Vanzi |first4=L |last5=Araya |first5=I |last6=Curé |first6=M |date=2018-01-03 |title=Stellar parameters and H α line profile variability of Be stars in the BeSOS survey |url=https://academic.oup.com/mnras/article/474/4/5287/4788120 |journal=Monthly Notices of the Royal Astronomical Society |volume=474 |issue=4 |pages=5287–5299 |doi=10.1093/mnras/stx3075 |doi-access=free |issn=0035-8711|arxiv=1711.08675 |bibcode=2018MNRAS.474.5287A }}</ref>
<ref name=Allen>{{citation | postscript=. | first=Richard Hinckley | last=Allen | year=1963 | orig-year=1899 | title=Star Names — Their Lore and Meaning | chapter=Centaurus | access-date=2025-12-06 | url=https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Centaurus*.html }}</ref>
<ref name=AEEA>{{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>
<ref name=zh>{{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>
<ref name=HipDataAccess>{{citation | postscript=. |title=Hipparcos Tools Interactive Data Access |url=https://www.cosmos.esa.int/web/hipparcos/interactive-data-access |website=Hipparcos |publisher=ESA |access-date=8 December 2021}}</ref>
<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=meilland2009>{{citation | postscript=. |bibcode=2008A&A...488L..67M |title=δ Centauri: A new binary be star detected by VLTI/AMBER spectro-interferometry | display-authors=1 |last1=Meilland |first1=A. |last2=Millour |first2=F. |last3=Stee |first3=Ph. |last4=Spang |first4=A. |last5=Petrov |first5=R. |last6=Bonneau |first6=D. |last7=Perraut |first7=K. |last8=Massi |first8=F. |journal=Astronomy and Astrophysics |date=2008 |volume=488 |issue=3 |pages=L67–L70 |doi=10.1051/0004-6361:200810624 |arxiv=0807.4622 |s2cid=118737029 }}</ref>
<ref name=Anderson2012>{{cite XHIP | 59196 | access-date=2025-12-06 | mode=cs2 | postscript=. }}</ref>
<ref name=rgcrv>{{citation | postscript=. | last1=Evans | first1=D. S. | date=June 20–24, 1966 | editor1-last=Batten | editor1-first=Alan Henry | editor2-last=Heard | editor2-first=John Frederick | title=The Revision of the General Catalogue of Radial Velocities | work=Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30 | volume=30 | pages=57 | location=University of Toronto | publisher=[[International Astronomical Union]] | bibcode=1967IAUS...30...57E }}</ref>
<ref name=aj84_1713>{{citation | last1=Feinstein | first1=A. | last2=Marraco | first2=H. G. | title=The photometric behavior of Be Stars | journal=Astronomical Journal | volume=84 | pages=1713–1725 |date=November 1979 | doi=10.1086/112600 | bibcode=1979AJ.....84.1713F | doi-access=free }}</ref>
<ref name=houk1979>{{citation | title=Michigan catalogue of two-dimensional spectral types for the HD stars | last1=Houk | first1=Nancy | publication-place=Ann Arbor, Michigan | publisher=Dept. of Astronomy, University of Michigan | date=1979 | bibcode=1978mcts.book.....H }}</ref>
<ref name=aaa505_2_687>{{citation | display-authors=1 | last1=Meilland | first1=A. | last2=Stee | first2=Ph. | last3=Chesneau | first3=O. | last4=Jones | first4=C. | title=VLTI/MIDI observations of 7 classical Be stars | journal=Astronomy and Astrophysics | volume=505 | issue=2 | pages=687–693 |date=October 2009 | doi=10.1051/0004-6361/200911960 | bibcode=2009A&A...505..687M |arxiv = 0908.1239 | s2cid=12694072 }}</ref>
<ref name=aaa488_3_L67>{{citation | display-authors=1 | last1=Meilland | first1=A. | last2=Millour | first2=F. | last3=Stee | first3=Ph. | last4=Spang | first4=A. | last5=Petrov | first5=R. | last6=Bonneau | first6=D. | last7=Perraut | first7=K. | last8=Massi | first8=F. | title=δ Centauri: a new binary Be star detected by VLTI/AMBER spectro-interferometry | journal=Astronomy and Astrophysics | volume=488 | issue=3 | pages=L67–L70 |date=September 2008 | doi=10.1051/0004-6361:200810624 | bibcode=2008A&A...488L..67M |arxiv = 0807.4622 | s2cid=118737029 | url=https://hal.archives-ouvertes.fr/hal-00307590 }}</ref>
<ref name=csiro>{{citation |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 |url-status=dead |archive-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archive-date=2012-03-18 }}</ref>
<ref name=aaa216_1_44>{{citation | display-authors=1 | last1=de Geus | first1=E. J. | last2=de Zeeuw | first2=P. T. | last3=Lub | first3=J. | title=Physical parameters of stars in the Scorpio-Centaurus OB association | journal=Astronomy and Astrophysics | volume=216 | issue=1–2 | pages=44–61 |date=June 1989 | bibcode=1989A&A...216...44D }}</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=gcvs>{{citation | postscript=. |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|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>
<ref name=levenhagen>{{citation | postscript=. | title=Spectroscopic analysis of southern B and Be stars | last1=Levenhagen | first1=R. S. | last2=Leister | first2=N. V. | journal=Monthly Notices of the Royal Astronomical Society | volume=371 | pages=252–262 | year=2006 | issue=1 | doi=10.1111/j.1365-2966.2006.10655.x | doi-access=free | arxiv=astro-ph/0606149 | bibcode=2006MNRAS.371..252L | s2cid=16492030 }}</ref>
<ref name=fremat>{{citation | postscript=. | title=Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars | journal=Astronomy and Astrophysics | volume=440 | issue=1 | pages=305–320 | year=2005 | last1=Frémat | first1=Y. | last2=Zorec | first2=J. | last3=Hubert | first3=A.-M. | last4=Floquet | first4=M. | bibcode=2005A&A...440..305F | doi=10.1051/0004-6361:20042229 | arxiv=astro-ph/0503381 | s2cid=19016751 | display-authors=1 }}</ref>
}}
{{Stars of Centaurus}}
<!-- Physical properties --> [[Category:B-type main-sequence stars]] [[Category:B-type subgiants]] [[Category:Be stars]] [[Category:Gamma Cassiopeiae variable stars]] [[Category:Lower Centaurus Crux]] <!-- Constellation & catalogues --> [[Category:Centaurus]] [[Category:Bayer objects|Centauri, Delta]] [[Category:Bright Star Catalogue objects|4621]] [[Category:Durchmusterung objects]] [[Category:Henry Draper Catalogue objects|105435]] [[Category:Hipparcos objects|059196]]