{{Short description|Variable star in the constellation Centaurus}} {{Starbox begin}} {{Starbox image | image = {{Location mark | image=Centaurus constellation map.svg | float=center | width=280 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=μ Cen | x=442 | y=448 }} | caption = Location of μ Centauri (circled) }} {{Starbox observe | epoch = [[J2000.0]] | constell = [[Centaurus]]<ref name=Anderson2012/> | ra = {{RA|13|49|36.98863}}<ref name=aaa474_2_653/> | dec = {{DEC|−42|28|25.4296}}<ref name=aaa474_2_653/> | appmag_v = {{nowrap|+3.42<ref name=apjs15_459/> (+2.92 to +3.49)<ref name=gcvs/>}} }} {{Starbox character | class = B2V:e<ref name=mk/> | b-v = −0.205<ref name=apjs15_459/> | u-b = −0.854<ref name=apjs15_459/> | variable = [[Gamma Cassiopeiae variable|γ Cas]]<ref name=gcvs/> }} {{Starbox astrometry | radial_v = +9.2{{±|2.7}}<ref name=Gontcharov_2006/> | prop_mo_ra = −24.25<ref name=aaa474_2_653/> | prop_mo_dec = −18.64 | pm_footnote = <ref name=aaa474_2_653/> | absmag_v = −2.48<ref name=Anderson2012/> | parallax = 6.45 | p_error = 0.16 | parallax_footnote = <ref name=aaa474_2_653/> }} {{Starbox detail | mass = {{val|9.1|0.2}}<ref name=mnras410_1_190/> | radius = 4.21 (equatorial)<br>{{Val|3.4|0.3}} (polar)<ref name=aaa369_1058/> | gravity = 3.86 (equatorial)<br>4.33 (polar)<ref name=aaa369_1058/> | metal_fe = | rotation = 11.615 hours<ref name=aaa369_1058/> | age_myr = {{val|19.8|1.7}}<ref name=mnras410_1_190/> | luminosity = 2,090<ref name=aaa369_1058/> | temperature = 17,600 (equatorial)<br>{{Val|23200|200|fmt=commas}} (polar)<ref name=aaa369_1058/> | rotational_velocity = 194<ref name=coapa239_1/> }} {{Starbox catalog | names = {{odlist | B=μ Cen | CD=−41°8172 | FK5=508 | HD=120324 | HIP=67472 | HR=5193 | SAO=224471 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad=HD+120324 }} {{Starbox end}}
'''Mu Centauri''' is a [[star]] in the southern [[constellation]] of [[Centaurus]]. Its name is a [[Bayer designation]] that is [[Romanization of Greek|Latinized]] from μ Centauri, and abbreviated Mu Cen or μ Cen. With the stars [[Nu Centauri|ν]] and [[Phi Centauri|φ Centauri]], it marks what has been traditionally portrayed as "''dextro Latere''" (the right side) of the Centaur.<ref name=Ptolemy/> The [[apparent visual magnitude]] of this star is 3.42,<ref name=apjs15_459/> making it one of the [[List of stars in Centaurus|brighter members]] of the constellation. The distance to this star can be estimated directly using [[stellar parallax|parallax]] measurements, which yield a value of roughly 510 [[light year]]s (155 [[parsec]]s) from [[Earth]].<ref name=aaa474_2_653/> It is drifting further away with a [[radial velocity]] of +9 km/s.<ref name=Gontcharov_2006/>
[[File:MuCenLightCurve.png|thumb|left|A [[Photometric_system#Photometric_letters|visual band]] [[light curve]] for Mu Centauri, plotted from data published by Aguayo ''et al.'' (2018)<ref name="Aguayo"/>]] The [[stellar spectrum|spectrum]] of Mu Centauri is considered to be a standard for a B2 [[Be star]] with the [[stellar classification]] of B2V:e.<ref name=mk/> The 'e' suffix is used to mark the presence of [[emission line]]s, caused by a circumstellar disk of hot gas that was formed from material ejected from the star. Mu Centauri is a pulsating variable star that has multiple non-radial cycles with a primary period of 0.503 days. Three other pulsation cycles have a similar period, while two have a shorter interval of about 0.28 days. It undergoes outburst events that result in the transfer of additional material to the surrounding disk.<ref name=aaa333_125/> During these outbursts, the star can experience transient periodicities.<ref name=aaa411_229/> Mu Centauri is classified as a [[Gamma Cassiopeiae variable|Gamma Cassiopeiae type]] [[variable star]] and its brightness varies from magnitude +2.92 to +3.49.<ref name=gcvs/>
This star is spinning rapidly, with a [[projected rotational velocity]] of 194<ref name=coapa239_1/> km s<sup>−1</sup> and is completing a full rotation in about 11.615 hours. The equatorial [[azimuth]]al velocity is around 85% of the critical velocity where the star would start to break up, resulting a pronounced [[equatorial bulge]] that is about 26% wider than the radius at the poles. Because of the [[oblate spheroid]]al shape of this star, the polar region is at a higher temperature than the equator—23,000 K versus 17,600 K respectively. Likewise, the gravitational force at the poles is greater than along the equator. The axis of rotation of the star is tilted by an angle of about (19 ± 3)° to the line of sight from the Earth.<ref name=aaa369_1058/>
At an estimated age of nearly 20 million years,<ref name=mnras410_1_190/> this star is around 55–65% of the way through its evolutionary period on the [[main sequence]] of core [[hydrogen burning]] stars.<ref name=aaa441_1_235/> It has around nine<ref name=mnras410_1_190/> times the mass of the Sun and four<ref name=aaa441_1_235/> times the Sun's radius, but emits over 2,000<ref name=aaa369_1058/> times as much energy as the Sun. The outer atmosphere has a mean [[effective temperature]] of 22,410 K,<ref name=aaa441_1_235/> giving the star a blue-white hue.<ref name=csiro/>
This star is a [[proper motion]] member of the Upper Centaurus–Lupus sub-group in the [[Scorpius–Centaurus association|Scorpius–Centaurus]] [[Stellar association|OB association]], the nearest such co-moving association of massive stars to the Sun.<ref name=aaa216_1_44/>
==References== {{reflist|30em|refs=
<ref name=aaa474_2_653>{{citation | postscript=. | 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 | 67472 | mode=cs2 | postscript=. }}</ref>
<ref name=SIMBAD>{{cite simbad | title=mu Cen | mode=cs2 | access-date=2025-12-16 | postscript=. }}</ref>
<ref name="Aguayo">{{citation | postscript=. | display-authors=1 |last1=Aguayo |first1=G. |last2=Mennickent |first2=R. E. |last3=Granada |first3=A. |last4=Otero |first4=S. |title=Multi-epoch L-band Spectroscopy of the Be Star μ Centauri Prior to Outburst |journal=The Astronomical Journal |date=October 2018 |volume=156 |issue=4 |page=174 |bibcode=2018AJ....156..174A |doi=10.3847/1538-3881/aad5db |s2cid=125167180 |doi-access=free |hdl=11336/82431 |hdl-access=free }}</ref>
<ref name=coapa239_1>{{citation | postscript=. | 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 | bibcode=1970CoAsi.239....1B }}</ref>
<ref name=mnras410_1_190>{{citation | postscript=. | 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=aaa441_1_235>{{citation | postscript=. | display-authors=1 | last1=Zorec | first1=J. | last2=Frémat | first2=Y. | last3=Cidale | first3=L. | title=On the evolutionary status of Be stars. I. Field Be stars near the Sun | journal=Astronomy and Astrophysics | volume=441 | issue=1 | pages=235–248 |date=October 2005 | doi=10.1051/0004-6361:20053051 | bibcode=2005A&A...441..235Z |arxiv = astro-ph/0509119 | s2cid=17592657 }}</ref>
<ref name=aaa411_229>{{citation | postscript=. | display-authors=1 | last1=Rivinius | first1=Th. | last2=Baade | first2=D. | last3=Štefl | first3=S. | title=Non-radially pulsating Be stars | journal=Astronomy and Astrophysics | volume=411 | pages=229–247 |date=November 2003 | issue=2 | doi=10.1051/0004-6361:20031285 | bibcode=2003A&A...411..229R | doi-access=free }}</ref>
<ref name=aaa369_1058>{{citation | postscript=. | display-authors=1 | last1=Rivinius | first1=Th. | last2=Baade | first2=D. | last3=Štefl | first3=S. | last4=Townsend | first4=R. H. D. | last5=Stahl | first5=O. | last6=Wolf | first6=B. | last7=Kaufer | first7=A. | title=Stellar and circumstellar activity of the Be star mu Centauri. III. Multiline nonradial pulsation modeling | journal=Astronomy and Astrophysics | volume=369 | pages=1058–1077 |date=April 2001 | doi=10.1051/0004-6361:20010185 | bibcode=2001A&A...369.1058R | doi-access=free }}</ref>
<ref name=aaa333_125>{{citation | postscript=. | display-authors=1 | last1=Rivinius | first1=Th. | last2=Baade | first2=D. | last3=Stefl | first3=S. | last4=Stahl | first4=O. | last5=Wolf | first5=B. | last6=Kaufer | first6=A. | title=Stellar and circumstellar activity of the Be star MU Centauri. I. Line emission outbursts | journal=Astronomy and Astrophysics | volume=333 | pages=125–140 |date=May 1998 | bibcode=1998A&A...333..125R }}</ref>
<ref name=csiro>{{citation | postscript=. | 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-url=https://web.archive.org/web/20120318151427/http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html | archive-date=March 18, 2012 | url-status=dead }}</ref>
<ref name=apjs15_459>{{citation | postscript=. | last1=Gutierrez-Moreno | first1=Adelina | last2=Moreno | first2=Hugo | title=A photometric investigation of the Scorpio-Centaurus association | journal=Astrophysical Journal Supplement | volume=15 | page=459 |date=June 1968 | bibcode=1968ApJS...15..459G | doi=10.1086/190168 | doi-access=free }}</ref>
<ref name=gcvs>{{citation | postscript=. | display-authors=1 | last1=Samus | first1=N. N. | last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=General Catalogue of Variable Stars | version=5.1 | journal=Astronomy Reports | year=2017 | volume=61 | issue=1 | pages=80–88 | bibcode=2017ARep...61...80S | s2cid=125853869 | doi=10.1134/S1063772917010085 }}</ref>
<ref name=aaa216_1_44>{{citation | postscript=. | 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=mk>{{citation | postscript=. | bibcode=1978rmsa.book.....M | title=Revised MK Spectral Atlas for stars earlier than the sun | journal=Williams Bay: Yerkes Observatory | display-authors=1 | last1=Morgan | first1=W. W. | last2=Abt | first2=Helmut A. | last3=Tapscott | first3=J. W. | year=1978 }}</ref>
<ref name=Ptolemy>{{citation | postscript=. | title=Star Catalogue of Ptolemy | website=The Astronomy Corner | url=http://astro.isi.edu/reference/almagest.html | access-date=2007-11-15 | archive-date=2007-11-15 | archive-url=https://web.archive.org/web/20071115020105/http://astro.isi.edu/reference/almagest.html | url-status=dead }}</ref>
<ref name=Gontcharov_2006>{{citation | postscript=. | title=Pulkovo compilation of radial velocities for 35495 stars in a common system | last=Gontcharov | first=G. A. | journal=[[Astronomy Letters]] | date=2006 | volume=32 | issue=11 | pages=759–771 | doi=10.1134/S1063773706110065 | arxiv=1606.08053 | bibcode=2006AstL...32..759G | s2cid=119231169 }}</ref>
}}
{{Stars of Centaurus}}
{{DEFAULTSORT:Mu Centauri}} <!-- Physical properties --> [[Category:B-type main-sequence stars]] [[Category:Gamma Cassiopeiae variable stars]] [[Category:Upper Centaurus Lupus]] <!-- Constellation & catalogues --> [[Category:Centaurus]] [[Category:Bayer objects|Centauri, Mu]] [[Category:Bright Star Catalogue objects|5193]] [[Category:Durchmusterung objects]] [[Category:Henry Draper Catalogue objects|120324]] [[Category:Hipparcos objects|067472]]