Mu Centauri

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Wikipedia

Mu Centauri
Location of μ Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus[1]
Right ascension 13h 49m 36.98863s[2]
Declination −42° 28′ 25.4296″[2]
Apparent magnitude (V) +3.42[3] (+2.92 to +3.49)[4]
Characteristics
Spectral type B2V:e[5]
U−B color index −0.854[3]
B−V color index −0.205[3]
Variable type γ Cas[4]
Astrometry
Radial velocity (Rv)+9.2±2.7[6] km/s
Proper motion (μ) RA: −24.25[2] mas/yr[2]
Dec.: −18.64 mas/yr[2]
Parallax (π)6.45±0.16 mas[2]
Distance510 ± 10 ly
(155 ± 4 pc)
Absolute magnitude (MV)−2.48[1]
Details
Mass9.1±0.2[7] M☉
Radius4.21 (equatorial)
3.4±0.3 (polar)[8] R☉
Luminosity2,090[8] L☉
Surface gravity (log g)3.86 (equatorial)
4.33 (polar)[8] cgs
Temperature17,600 (equatorial)
23,200±200 (polar)[8] K
Rotation11.615 hours[8]
Rotational velocity (v sin i)194[9] km/s
Age19.8±1.7[7] Myr
Other designations
μ Cen, CD−41°8172, FK5 508, HD 120324, HIP 67472, HR 5193, SAO 224471[10]
Database references
SIMBADdata

Mu Centauri is a star in the southern constellation of Centaurus. Its name is a Bayer designation that is Latinized from μ Centauri, and abbreviated Mu Cen or μ Cen. With the stars ν and φ Centauri, it marks what has been traditionally portrayed as "dextro Latere" (the right side) of the Centaur.[11] The apparent visual magnitude of this star is 3.42,[3] making it one of the brighter members of the constellation. The distance to this star can be estimated directly using parallax measurements, which yield a value of roughly 510 light years (155 parsecs) from Earth.[2] It is drifting further away with a radial velocity of +9 km/s.[6]

A visual band light curve for Mu Centauri, plotted from data published by Aguayo et al. (2018)[12]

The spectrum of Mu Centauri is considered to be a standard for a B2 Be star with the stellar classification of B2V:e.[5] The 'e' suffix is used to mark the presence of emission lines, 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.[13] During these outbursts, the star can experience transient periodicities.[14] Mu Centauri is classified as a Gamma Cassiopeiae type variable star and its brightness varies from magnitude +2.92 to +3.49.[4]

This star is spinning rapidly, with a projected rotational velocity of 194[9] km s−1 and is completing a full rotation in about 11.615 hours. The equatorial azimuthal 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 spheroidal 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.[8]

At an estimated age of nearly 20 million years,[7] this star is around 55–65% of the way through its evolutionary period on the main sequence of core hydrogen burning stars.[15] It has around nine[7] times the mass of the Sun and four[15] times the Sun's radius, but emits over 2,000[8] times as much energy as the Sun. The outer atmosphere has a mean effective temperature of 22,410 K,[15] giving the star a blue-white hue.[16]

This star is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[17]

References

  1. 1 2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 6 7 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  3. 1 2 3 4 Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168.
  4. 1 2 3 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. 1 2 Morgan, W. W.; et al. (1978), "Revised MK Spectral Atlas for stars earlier than the sun", Williams Bay: Yerkes Observatory, Bibcode:1978rmsa.book.....M.
  6. 1 2 Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  7. 1 2 3 4 Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  8. 1 2 3 4 5 6 7 Rivinius, Th.; et al. (April 2001), "Stellar and circumstellar activity of the Be star mu Centauri. III. Multiline nonradial pulsation modeling", Astronomy and Astrophysics, 369: 1058–1077, Bibcode:2001A&A...369.1058R, doi:10.1051/0004-6361:20010185.
  9. 1 2 Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1), Bibcode:1970CoAsi.239....1B.
  10. ↑ "mu Cen", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2025-12-16.
  11. ↑ "Star Catalogue of Ptolemy", The Astronomy Corner, archived from the original on 2007-11-15, retrieved 2007-11-15.
  12. ↑ Aguayo, G.; et al. (October 2018), "Multi-epoch L-band Spectroscopy of the Be Star μ Centauri Prior to Outburst", The Astronomical Journal, 156 (4): 174, Bibcode:2018AJ....156..174A, doi:10.3847/1538-3881/aad5db, hdl:11336/82431, S2CID 125167180.
  13. ↑ Rivinius, Th.; et al. (May 1998), "Stellar and circumstellar activity of the Be star MU Centauri. I. Line emission outbursts", Astronomy and Astrophysics, 333: 125–140, Bibcode:1998A&A...333..125R.
  14. ↑ Rivinius, Th.; et al. (November 2003), "Non-radially pulsating Be stars", Astronomy and Astrophysics, 411 (2): 229–247, Bibcode:2003A&A...411..229R, doi:10.1051/0004-6361:20031285.
  15. 1 2 3 Zorec, J.; et al. (October 2005), "On the evolutionary status of Be stars. I. Field Be stars near the Sun", Astronomy and Astrophysics, 441 (1): 235–248, arXiv:astro-ph/0509119, Bibcode:2005A&A...441..235Z, doi:10.1051/0004-6361:20053051, S2CID 17592657.
  16. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16.
  17. ↑ de Geus, E. J.; et al. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D.