Eta Canis Majoris
 Eta Canis Majoris, a blue Supergiant in Canis Major |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 24m 05.70228s[1] |
| Declination | –29° 18′ 11.1798″[1] |
| Apparent magnitude (V) | 2.450[2] |
| Characteristics | |
| Spectral type | B5 Ia[3] |
| U−B color index | -0.708[2] |
| B−V color index | -0.087[2] |
| Variable type | α Cyg[citation needed] |
| Astrometry | |
| Radial velocity (Rv) | 41.1[4] km/s |
| Proper motion (μ) | RA: -4.14[1] mas/yr Dec.: 5.81[1] mas/yr |
| Parallax (π) | 1.64 ± 0.40[1] mas |
| Distance | approx. 2,000 ly (approx. 600 pc) |
| Details | |
| Mass | 19.19 ± 1.15[5] M☉ |
| Radius | 56.3[6] R☉ |
| Luminosity | 105,442[5] L☉ |
| Temperature | 15,000[3] K |
| Rotational velocity (v sin i) | 50[7] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Eta Canis Majoris (η CMa, η Canis Majoris) is a star in the constellation Canis Major. It has the traditional name Aludra. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[8]
The name Aludra originates from the Arabic: عذرا al-‘aðrā "the virgin". This star, along with ε CMa (Adhara), δ CMa (Wezen) and ο2 CMa (Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.[9]
In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow,[10] refers to an asterism consisting of η Canis Majoris, δ Canis Majoris, c Puppis, ZI 674, ο Puppis, κ Puppis, ε Canis Majoris, κ Canis Majoris and π Puppis.[11] Consequently, δ Canis Majoris itself is known as 弧矢二 (Hú Shǐ èr, English: the Second Star of Bow and Arrow.)[12]
[edit] Properties
Aludra shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter (absolute magnitude) than the Sun. A blue supergiant, Aludra has only been around a fraction of the time our Sun has, yet is already in the last stages of its life. It is still expanding and may become a red supergiant, or perhaps has already passed that phase, but in either case it will become a supernova within the next few million years.
η Canis Majoris is classified as an Alpha Cygni type[citation needed] variable star and its brightness varies from magnitude +2.38 to +2.48.
[edit] Namesakes
Both USS Aludra (AF-55) and USS Aludra (AK-72), a Crater class cargo ship, were United States Navy vessels named after the constellation.
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- ^ a b c Alcaino, Gonzalo (June 1969), "The Globular Clusters NGC 2808 and NGC 1851", Astrophysical Journal 156: 853, Bibcode 1969ApJ...156..853A, doi:10.1086/150019
- ^ a b Prinja, R. K.; Massa, D. L. (October 2010), "Signature of wide-spread clumping in B supergiant winds", Astronomy and Astrophysics 521, Bibcode 2010A&A...521L..55P, doi:10.1051/0004-6361/201015252
- ^ Wielen, R. et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions, Astronomisches Rechen-Institut Heidelberg, Bibcode 1999VeARI..35....1W
- ^ a b Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, Bibcode 2010AN....331..349H, doi:10.1002/asna.200911355
- ^ Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode 1979MNRAS.189..601U
- ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1 pages=359–365), Bibcode 2002ApJ...573..359A, doi:10.1086/340590
- ^ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society 25: 1319, Bibcode 1993AAS...183.1710G, http://www.astro.utoronto.ca/~garrison/mkstds.html, retrieved 2012-02-04
- ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 130, ISBN 0486210790, http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Canis_Major*.html, retrieved 2010-12-12
- ^ 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen had opinion that Koo She refers to the asterism including δ Velorum and ω Velorum. AEEA opinion is, δ Velorum is member of 天社 (Tiān Shè), meaning Celestial Earth God's Temple asterism and ω Velorum is not member of any asterisms. 天社 (Tiān Shè) is westernized into Tseen She and R.H.Allen used the term Tseen She for Chinese name of η Carinae. See Richard Hinckley Allen: Star Names — Their Lore and Meaning: Argo Navis and (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 17 日.
- ^ (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 9789867332257.
- ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
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