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Eta Centauri

From Wikipedia, the free encyclopedia
Star in the constellation Centaurus
Not to be confused withH Centauri.
Eta Centauri
Location of η Centauri (circled)
Observation data
EpochJ2000.0      EquinoxJ2000.0
ConstellationCentaurus
Right ascension14h 35m 30.42416s[1]
Declination−42° 09′ 28.1708″[1]
Apparent magnitude (V)+2.35[2](2.30 - 2.41[3])
Characteristics
Spectral typeB1.5 Vne[4]
U−Bcolor index−0.862[2]
B−Vcolor index−0.215[2]
Variable typeGCAS[3] +LERI
Astrometry
Radial velocity (Rv)−0.2[5] km/s
Proper motion (μ)RA: −34.73[1]mas/yr
Dec.: −32.72[1]mas/yr
Parallax (π)10.67±0.21 mas[1]
Distance306 ± 6 ly
(94 ± 2 pc)
Absolute magnitude (MV)−2.53[6]
Details
Mass12.0±0.3[7] M☉
Radius6.10±0.12[8] R☉
Luminosity8,700[4] L☉
Surface gravity (log g)3.95±0.04[8] cgs
Temperature25,700[4] K
Rotational velocity (v sin i)330[4] km/s
Age5.6±1.0[7] Myr
Other designations
η Cen,CD−41°8917,CPD−41°6839,FK5 537,HD 127972,HIP 71352,HR 5440,SAO 225044.[9]
Database references
SIMBADdata

Eta Centauri,Latinized from η Centauri, is astar in the southernconstellation ofCentaurus. It has anapparent visual magnitude of +2.35[2] and is located at a distance of around 306light-years (94parsecs).[1]

Alight curve for Eta Centauri, plotted fromTESS data[10]

Thestellar classification of this star is B1.5 Vne,[4] indicating that it is aB-type main sequence star. The 'n' suffix means that theabsorption lines are broadened from rapid rotation and the 'e' that it showsemission lines in its spectrum. It has aprojected rotational velocity of 330 km s−1[4] and completes a full rotation in less than a day.

As aBe star,[11] it has variable emissions in itshydrogen spectral lines. This emission can be modelled by adecretion disk of gas that has been ejected from the star by its rapid rotation and now follows a near-Keplerian orbit around the central body.[12] Its brightness is also slightly variable, and it is classified as aGamma Cassiopeiae variable star with multiple periods of variability.[3] The International Variable Star Index lists Eta Centauri as both a Gamma Cassiopeiae variable and a Lambda Eridani variable with variations caused by its rotation and pulsations.[13]

Eta Centauri has about 12 times the mass of the Sun,[7] placing it above the dividing line between stars that evolve intowhite dwarfs and those that turn intosupernovae. It is radiating 8,700[4] times theluminosity of the Sun from itsouter atmosphere at aneffective temperature of 25,700 K.[4] At this temperature, the star glows with the blue-white hue common toB-type stars.[14] Eta Centauri is aproper motion member of the Upper Centaurus–Lupus sub-group in theScorpius–CentaurusOB association, the nearest such co-moving association of massive stars to the Sun.[15]

In traditionalChinese astronomy, Eta Centauri was known as庫樓二[16] (meaning: the Second (Star) ofKoo Low).[17]

References

[edit]
  1. ^abcdefvan 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.
  2. ^abcdGutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association",Astrophysical Journal Supplement Series,15: 459,Bibcode:1968ApJS...15..459G,doi:10.1086/190168.
  3. ^abcSamus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)",VizieR On-line Data Catalog: B/gcvs,1: 02025,Bibcode:2009yCat....102025S.
  4. ^abcdefghBalona, 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.
  5. ^Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions",Veröff. Astron. Rechen-Inst. Heidelb,35 (35), Astronomisches Rechen-Institut Heidelberg: 1,Bibcode:1999VeARI..35....1W.
  6. ^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,S2CID 119257644.
  7. ^abcTetzlaff, 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,S2CID 118629873.
  8. ^abArcos, C.; et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey",Monthly Notices of the Royal Astronomical Society,474 (4):5287–5299,arXiv:1711.08675,Bibcode:2018MNRAS.474.5287A,doi:10.1093/mnras/stx3075.
  9. ^"eta Cen",SIMBAD,Centre de données astronomiques de Strasbourg, retrieved2012-03-03.
  10. ^MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved8 December 2021.
  11. ^Janot-Pacheco, E., Leister NV, et al. (1999), "Multi-periodicity of the Be star η Centauri from spectroscopic and photometric observations",Astronomy and Astrophysics Supplement Series,137 (3): 407,Bibcode:1999A&AS..137..407J,doi:10.1051/aas:1999256.
  12. ^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",Astrophysical Journal Supplement Series,187 (1):228–250,Bibcode:2010ApJS..187..228S,doi:10.1088/0067-0049/187/1/228,S2CID 122679154.
  13. ^Watson, C. L. (2006), "The International Variable Star Index (VSX)",The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25,25: 47,Bibcode:2006SASS...25...47W.
  14. ^"The Colour of Stars",Australia Telescope, Outreach and Education,Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived fromthe original on 2012-03-18, retrieved2012-01-16.
  15. ^de Geus, E. J.; de Zeeuw, P. T.; 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.
  16. ^(in 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.
  17. ^Allen, R. H. (1963),Star Names: Their Lore and Meaning (Reprint ed.),New York,NY:Dover Publications Inc., p. 154,ISBN 0-486-21079-0.

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