Epsilon Canis Majoris
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Canis Major |
| Right ascension | 06h 58m 37.6s |
| Declination | –28° 58′ 19″ |
| Apparent magnitude (V) | 1.50 |
| Characteristics | |
| Spectral type | B2 Iab |
| U−B color index | –0.93 |
| B−V color index | –0.13 |
| Astrometry | |
| Radial velocity (Rv) | +27.3 km/s |
| Proper motion (μ) | RA: +2.63 mas/yr Dec.: +2.29 mas/yr |
| Parallax (π) | 7.57 ± 0.57 mas |
| Distance | 430 ± 30 ly (132 ± 10 pc) |
| Absolute magnitude (MV) | –4.11 |
| Details | |
| Mass | 10.1 ± 1.0[1] M☉ |
| Radius | 12.7[2] R☉ |
| Luminosity | 47,000[3] L☉ |
| Surface gravity (log g) | 3.39[3] |
| Temperature | 22,900[3] K |
| Age | 22.5 ± 2.6[1] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon Canis Majoris (ε CMa, ε Canis Majoris) is the second brightest star in the constellation Canis Major, and one of the brightest stars in the night sky. It has the Bayer designation "epsilon" despite being the second brightest and not the fifth brightest star in its constellation. It has the traditional name Adhara (sometimes spelled Adara). The name is from the Arabic word عذارى ‘aðāra’, "virgins".
In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow,[4] refers to an asterism consisting of ε Canis Majoris, δ Canis Majoris, η Canis Majoris, c Puppis, ZI 674, ο Puppis, κ Puppis, κ Canis Majoris and π Puppis.[5] Consequently, ε Canis Majoris itself is known as 弧矢七 (Hú Shǐ qī, English: the Seventh Star of Bow and Arrow.)[6]
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Adzari (أول ألعذاري - awwil al-aðārii), which was translated into Latin as Prima Virginum, meaning First of the Virgins.[7] This star, along with δ CMa (Wezen), η CMa (Aludra) and ο2 CMa (Thanih al Adzari), were Al ʽAdhārā (ألعذاري), the Virgins.[8][9]
Contents |
[edit] Properties
Adhara is a binary star, about 430 light years away from Earth.[10] The main star possesses an apparent magnitude of +1.5 and belongs to the spectral classification B2. Its color is blue or blueish-white, due to the surface temperature of 22,900 K. It emits a total radiation equal to 47,000 times that of the Sun. This star is one of the brightest known extreme ultraviolet sources in the sky.[11] It is the strongest source of photons capable of ionizing hydrogen atoms in interstellar gas near the sun, and is very important in determining the ionization state of the Local Interstellar Cloud.[12]
The +7.5 magnitude companion star (the absolute magnitude amounts to +1.9) is at 7.5" away with a position angle of 161° of the main star. Despite the relatively large angular distance the components can only be resolved in large telescopes, since the main star is approximately 250 times brighter than its companion.
A few million years ago, Adhara was much closer to the Sun than it is at present, causing it to be a much brighter star in the night sky. About 4,700,000 years ago, Adhara was 34 light years from the Sun, and was the brightest star in the sky with a magnitude of –3.99. No other star has attained this brightness since, nor will any other star attain this brightness for at least five million years.[13]
[edit] Modern legacy
Adhara appears on the national flag of Brazil, symbolising the state of Tocantins.[14]
[edit] Namesakes
USS Adhara (AK-71) was a United States Navy Crater class cargo ship named after the star.
[edit] See also
[edit] References
- ^ a b 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, Bibcode 2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x
- ^ 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
- ^ a b c Lyubimkov, L. S.; Rostopchin, S. I.; Lambert, D. L. (June 2004), "Surface abundances of light elements for a large sample of early B-type stars - III. An analysis of helium lines in spectra of 102 stars", Monthly Notices of the Royal Astronomical Society 351 (2): 745–767, Bibcode 2004MNRAS.351..745L, doi:10.1111/j.1365-2966.2004.07825.x
- ^ 弧矢 (Hú Shǐ) is westernized into Koo She. R.H. Allen opined 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.
- ^ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society 55: 429. Bibcode 1895MNRAS..55..429K.
- ^ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: 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.
- ^ ε CMa as Aoul al Adzari or Prima Virginum (First of the Virgins), ο2 CMa as Thanih al Adzari or Secunda Virginum (Second of the Virgins) and δ CMa as Thalath al Adzari or Tertia Virginum (Third of the Virgins). η CMa should be Rabah al Adzari or Quarta Virginum (Fourth of the Virgins) consistently, but it was given by the name Aludra, meaning Virgin (same meaning with Adhara (ε CMa) or Al ʽAdhārā)
- ^ http://www.daviddarling.info/encyclopedia/A/Adhara.html
- ^ Wilkinson, E.; Green, J. C., McLean, R., Welsh, B. (May 1996). "Extreme ultraviolet spectrum of ɛ Canis Majoris between 600-920 Å". Bull. American Astron. Soc. 28 (2): 915. Bibcode 1996BAAS...28..915W.
- ^ Vallerga, J. V.; Welsh, B. Y. (1995). "Epsilon Canis Majoris and the ionization of the local cloud". Astrophys. J. 444: 702–707. Bibcode 1995ApJ...444..702V. doi:10.1086/175643.
- ^ Sky and Telescope, April 1998.
- ^ "Astronomy of the Brazilian Flag". FOTW Flags Of The World website. http://www.fotw.net/flags/br_astro.html.
|
|||||||||||||||||
