Epoch J2000.0 Equinox J2000.0
|Right ascension||14h 35m 30.42416s|
|Declination||−42° 09′ 28.1708″|
|Apparent magnitude (V)||+2.35|
|Spectral type||B1.5 Vne|
|U−B color index||−0.862|
|B−V color index||−0.215|
|Variable type||Gamma Cas|
|Radial velocity (Rv)||–0.2 km/s|
|Proper motion (μ)||RA: −34.73 mas/yr
Dec.: −32.72 mas/yr
|Parallax (π)||10.67 ± 0.21 mas|
|Distance||306 ± 6 ly
(94 ± 2 pc)
|Mass||12.0 ± 0.3 M☉|
|Surface gravity (log g)||3.20 cgs|
|Rotational velocity (v sin i)||330 km/s|
|Age||5.6 ± 1.0 Myr|
Eta Centauri (η Cen, η Centauri) is a star in the southern constellation of Centaurus. It has an apparent visual magnitude of +2.35 and is located at a distance of around 306 light-years (94 parsecs). In traditional Chinese astronomy, Eta Centauri was known as 庫樓二 (meaning: the Second (Star) of Koo Low).
The stellar classification of this star is B1.5 Vne, indicating that it is a B-type main sequence star. The 'n' suffix means that the absorption lines are broadened from rapid rotation. It has a projected rotational velocity of 330 km s−1 and completes a full rotation in less than a day. This is a Be star as shown by the 'e' suffix, which means it has variable emissions in its hydrogen spectral lines. This emission can be modeled by a decretion disk of gas that has been ejected from the star and now follows a near Keplerian orbit around the central body. Finally it is slightly variable, and classified as a Gamma Cassiopeiae variable star with multiple periods of variability.
Eta Centauri has about 12 times the mass of the Sun, placing it above the dividing line between stars that evolve into white dwarfs and those that turn into supernovae. It is radiating 8,700 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 25,700 K. This heat causes the star to glow with the blue-white hue common to B-type stars. Eta Centauri 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.
- 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.
- 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
- Balona, L. A.; Dziembowski, W. A. (October 1999), "Excitation and visibility of high-degree modes in stars", Monthly Notices of the Royal Astronomical Society 309 (1): 221–232, Bibcode:1999MNRAS.309..221B, doi:10.1046/j.1365-8711.1999.02821.x
- Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W
- Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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
- de Geus, P. T.; de Zeeuw; Lub, J. (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
- "eta Cen -- Be Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-03-03
- (Chinese) 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.
- Allen, R. H. (1963), Star Names: Their Lore and Meaning (rep. ed.), New York, NY: Dover Publications Inc., p. 154, ISBN 0-486-21079-0
- Janot-Pacheco, E., Leister, N. V. et al. (1999), "Multi-periodicity of the Be star η Centauri from spectroscopic and photometric observations", A&AS 137 (3): 407, Bibcode:1999A&AS..137..407J, doi:10.1051/aas:1999256
- Silaj, J.; Jones, C. E.; Tycner, C.; Sigut, T. A. A.; Smith, A. D. (March 2010), "A Systematic Study of Hα Profiles of Be Stars", The Astrophysical Journal Supplement 187 (1, pp. 228–250), Bibcode:2010ApJS..187..228S, doi:10.1088/0067-0049/187/1/228
- "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16
- Eta Centauri by Jim Kaler.