Delta Centauri

From Wikipedia, the free encyclopedia
Jump to: navigation, search
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]
Characteristics
Spectral type B2 IVne[3]
U−B color index −0.92[2]
B−V color index −0.13[2]
Variable type γ Cas
Astrometry
Radial velocity (Rv) +11[4] 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
Distance 410 ± 20 ly
(127 ± 8 pc)
Details
Mass 8.6 ± 0.3[5] M
Radius 5.9 ± 0.5[5] R
Luminosity 5,000[5] L
Surface gravity (log g) 3.94 ± 0.05[5] cgs
Temperature 22384 ± 446[5] K
Rotational velocity (v sin i) 263 ± 14[5] km/s
Age 21.5 ± 1.5[6] Myr
Other designations
CD−50°6697, CPD−50°4862, FK5 452, HD 105435, HIP 59196, HR 4621, SAO 239689.

Delta Centauri (δ Cen, 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]

Delta Centauri is a variable star with a brightness varies from magnitude +2.51 to +2.65. This variability can be successfully modeled as a Gamma Cassiopeiae type variable,[5] also known as a shell star. 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.[7] It has a radius of 5.9 times the radius of the Sun[8] and 8.6 times the Sun's mass.[8]

The stellar classification of this star is B2 IVne,[3] 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.[5] Delta 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.[5] 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.[9]

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.[10] Consequently, δ Centauri itself is known as 馬尾三 (Mǎ Wěi sān, English: the Third Star of Horse's Tail.).[11] From this Chinese name, the name Ma Wei was appeared.[12]

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).[13]

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 Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H 
  4. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; John Frederick, Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E 
  5. ^ a b c d e f g h i 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 
  6. ^ 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 
  7. ^ The Colour of Stars, Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  8. ^ a b c 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. ^ 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 
  10. ^ (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.
  11. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
  12. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Centaurus
  13. ^ p. 8, Explorers of the southern sky: a history of Australian astronomy, Raymond Haynes, Cambridge, Cambridge University Press, 1996.