Epsilon Canis Majoris
 Location of ε Canis Majoris (circled) |
|
| 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 | B2II |
| U−B color index | –0.93 |
| B−V color index | –0.21 |
| 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 ± 0.57mas |
| Distance | 430 ± 30 ly (132 ± 10 pc) |
| Absolute magnitude (MV) | –4.8 |
| Details | |
| Mass | 12.6 ± 1.0 M☉ |
| Radius | 13.9 R☉ |
| Luminosity | 38,700 L☉ |
| Surface gravity (log g) | 3.39 cgs |
| Temperature | 22,900 K |
| Rotational velocity (v sin i) | 25 km/s |
| Age | 22.5 ± 2.6 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Epsilon Canis Majoris (ε Canis Majoris, abbreviated Epsilon CMa, ε CMa), also named Adhara, is a binary star and, despite being designated 'epsilon', the second brightest star in the constellation of Canis Major and one of the brightest stars in the night sky. About 4.7 million years ago, it was the brightest star in the sky, with an apparent magnitude of -3.99.
ε Canis Majoris (Latinised to Epsilon Canis Majoris) is the star's Bayer designation.
It bore the traditional name Adhara (sometimes spelled Adara), derived from the Arabic word عذارى ‘aðāra’, "virgins". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Adhara for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In the 17th century catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Adzari (أول العذاري - awwal al-adhara), which was translated into Latin as Prima Virginum, meaning First of the Virgins. Along with Delta Canis Majoris (Wezen), Eta Canis Majoris (Aludra) and Omicron² Canis Majoris (Thanih al Adzari), these stars were Al ʽAdhārā (العذاري), 'the Virgins'.
In Chinese, 弧矢 (Hú Shǐ), meaning Bow and Arrow, refers to an asterism consisting of Epsilon Canis Majoris, Delta Canis Majoris, Eta Canis Majoris, HD 63032, HD 65456, Omicron Puppis, k Puppis, Kappa Canis Majoris and Pi Puppis. Consequently, Epsilon Canis Majoris itself is known as 弧矢七 (Hú Shǐ qī, English: the Seventh Star of Bow and Arrow).
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