Delta Centauri

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δ Centauri
Diagram showing star positions and boundaries of the Centaurus constellation and its surroundings
Cercle rouge 100%.svg
Location of δ Centauri (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension  12h 08m 21.49764s[1]
Declination −50° 43′ 20.7386″[1]
Apparent magnitude (V) +2.57[2] (2.51 - 2.65[3])
Characteristics
Spectral type B2 IVne[4]
U−B color index −0.92[2]
B−V color index −0.13[2]
Variable type γ Cas[3]
Astrometry
Radial velocity (Rv)+11[5] km/s
Proper motion (μ) RA: −49.94[1] mas/yr
Dec.: −7.19[1] mas/yr
Parallax (π)7.86 ± 0.47[1] mas
Distance410 ± 20 ly
(127 ± 8 pc)
Absolute magnitude (MV)−2.94[6]
Details
Mass8.7 ± 0.3[7] M
Radius6.5[8] R
Luminosity5,129[7] L
Surface gravity (log g)3.92[8] cgs
Temperature22,360[8] K
Rotational velocity (v sin i)263 ± 14[9] km/s
Age21.5 ± 1.5[10] Myr
Other designations
δ Cen, CD−50°6697, CPD−50°4862, FK5 452, HD 105435, HIP 59196, HR 4621, SAO 239689.
Database references
SIMBADdata

Delta Centauri, Latinized from δ Centauri, is a star in the southern constellation of Centaurus. The apparent visual magnitude of this star is +2.57,[2] making it readily visible to the naked eye. Based upon parallax measurements, it is located at a distance of about 410 light-years (130 parsecs) from the Earth.[1]

Properties[edit]

δ Centauri is a shell star, with a distinctive 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 γ Cassiopeiae type variable;[11] 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.[12] It has a radius of 6.5 times the radius of the Sun[8] and 8.7 times the Sun's mass.[8]

The stellar classification of this star is B2 IVne,[4] with the luminosity class of IV indicating that this is a subgiant star that has exhausted the hydrogen at its core and begun to evolve away from the main sequence; the star is spinning rapidly, with the resulting Doppler effect giving its spectrum broad absorption lines 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 and is surrounded by circumstellar gas; the presence of this gas creates an excess emission of infrared, along with emission lines in the star's spectrum. Most of it is concentrated around the equator, forming a disk.[8]

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 Units.[11] 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.[11] It is a proper motion member of the Lower-Centaurus Crux sub-group in the Scorpius-Centaurus OB association, the nearest such of association of co-moving massive stars to the Sun.[13]

Etymology[edit]

In Chinese, 馬尾 (Mǎ Wěi), meaning Horse's Tail, refers to an asterism consisting of δ Centauri, G Centauri and ρ Centauri.[14] Consequently, δ Centauri itself is known as 馬尾三 (Mǎ Wěi sān, English: the Third Star of Horse's Tail.).[15] From this Chinese name, the name Ma Wei was appeared.[16]

The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named Iritjinga, "The Eagle-hawk", a quadrangular arrangement comprising this star, γ Cen (Muhlifain), γ Cru (Gacrux), and δ Cru (Palida).[17]

See also[edit]

References[edit]

  1. ^ a b c d e f 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
  2. ^ a b c d Feinstein, A.; Marraco, H. G. (November 1979), "The photometric behavior of Be Stars", Astronomical Journal, 84: 1713–1725, Bibcode:1979AJ.....84.1713F, doi:10.1086/112600
  3. ^ a b Samus, 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. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. ^ a b Houk, Nancy (1979), "Michigan catalogue of two-dimensional spectral types for the HD stars", Ann Arbor : Dept. of Astronomy, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H
  5. ^ Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and their Applications. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
  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.
  7. ^ a b Levenhagen, R. S.; Leister, N. V. (2006). "Spectroscopic analysis of southern B and Be stars". Monthly Notices of the Royal Astronomical Society. 371: 252–262. arXiv:astro-ph/0606149. Bibcode:2006MNRAS.371..252L. doi:10.1111/j.1365-2966.2006.10655.x.
  8. ^ a b c d e f Meilland, A.; et al. (October 2009), "VLTI/MIDI observations of 7 classical Be stars", Astronomy and Astrophysics, 505 (2): 687–693, arXiv:0908.1239, Bibcode:2009A&A...505..687M, doi:10.1051/0004-6361/200911960
  9. ^ Frémat, Y.; Zorec, J.; Hubert, A.-M.; Floquet, M. (2005). "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars". Astronomy and Astrophysics. 440 (1): 305–320. arXiv:astro-ph/0503381. Bibcode:2005A&A...440..305F. doi:10.1051/0004-6361:20042229.
  10. ^ 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
  11. ^ a b c Meilland, A.; et al. (September 2008), "δ Centauri: a new binary Be star detected by VLTI/AMBER spectro-interferometry", Astronomy and Astrophysics, 488 (3): L67–L70, arXiv:0807.4622, Bibcode:2008A&A...488L..67M, doi:10.1051/0004-6361:200810624
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16
  13. ^ 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
  14. ^ ‹See Tfd›(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.
  15. ^ ‹See Tfd›(in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
  16. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Centaurus
  17. ^ Raymond Haynes; Roslynn D. Haynes; David Malin; Richard McGee (1996). Explorers of the Southern Sky: A History of Australian Astronomy. Cambridge University Press. p. 8. ISBN 978-0-521-36575-8.