Omega Carinae

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Omega Carinae
Diagram showing star positions and boundaries of the Carina constellation and its surroundings
Cercle rouge 100%.svg

Location of ω Carinae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Carina
Right ascension 10h 13m 44.21739s[1]
Declination –70° 02′ 16.4563″[1]
Apparent magnitude (V) 3.29[2]
Characteristics
Spectral type B8 IIIe[3]
U−B color index –0.285[4]
B−V color index –0.083[4]
Astrometry
Radial velocity (Rv) +7.0[2] km/s
Proper motion (μ) RA: -36.01[1] mas/yr
Dec.: +7.09[1] mas/yr
Parallax (π) 9.54 ± 0.09[1] mas
Distance 342 ± 3 ly
(104.8 ± 1.0 pc)
Details
Surface gravity (log g) 3.581[5] cgs
Temperature 13,275[5] K
Rotational velocity (v sin i) 245[5] km/s
Other designations
HR 4037, HD 89080, CP−69°1178, FK5 385, HIP 50099, SAO 250885.[6]

Omega Carinae (ω Car, ω Carinae) is a star in the constellation Carina. With a declination greater than 70 degrees south of the celestial equator, it is the most southerly of the bright stars of Carina (third-magnitude or brighter), and it is part of a southern asterism known as the Diamond Cross. This star has an apparent visual magnitude of 3.3[2] and is located at a distance of about 342 light-years (105 parsecs) from Earth.[1]

Properties[edit]

Omega Carinae has a stellar classification of B8 IIIe,[3] which places it among a category known as Be stars that display emission lines of hydrogen their spectrum. Omega Carinae is a shell star,[3] having a circumstellar disk of gas surrounding its equator. The luminosity class of III indicates it has evolved into a giant star, having exhausted the hydrogen at its core and left the main sequence. The effective temperature of 13,275 K[5] in its outer envelope is what gives this star the blue-white hue that is characteristic of B-type stars.

This star is rotating rapidly with a projected rotational velocity of 245 km s−1, which gives a lower limit to the star's azimuthal velocity along the equator. The critical equatorial velocity, at which the star would begin to break up, is 320 km s−1. The star's axis of rotation is inclined by an estimated angle of 70.8° to the line of sight from the Earth.[5]

In the next 7500 years, the south Celestial pole will pass close to this stars and I Carinae (5800 CE).[7]

In culture[edit]

In Chinese, 南船 (Nán Chuán), meaning Southern Boat, refers to an asterism consisting of ω Carinae, V337 Carinae, PP Carinae, θ Carinae and β Carinae .[8] Consequently, ω Carinae itself is known as 南船四 (Nán Chuán sì, English: the Fourth Star of Southern Boat.)[9]

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 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 
  3. ^ a b c Rivinius, Th.; Štefl, S.; Baade, D. (November 2006), "Bright Be-shell stars", Astronomy and Astrophysics 459 (1): 137–145, Bibcode:2006A&A...459..137R, doi:10.1051/0004-6361:20053008 
  4. ^ a b 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 
  5. ^ a b c d e Frémat, Y. et al. (September 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 
  6. ^ "ome Car -- Be Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-13 
  7. ^ http://myweb.tiscali.co.uk/moonkmft/Articles/Precession.html
  8. ^ (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.
  9. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 28 日

External links[edit]