Epsilon Canis Majoris
Epsilon Canis Majoris is a binary star system and the second-brightest object in the constellation of Canis Major. Its name is a Bayer designation that is Latinised from ε Canis Majoris, and abbreviated Epsilon CMa or ε CMa. This is the 22nd-brightest star in the night sky with an apparent magnitude of 1.50. About 4.7 million years ago, it was the brightest star in the night sky, with an apparent magnitude of −3.99. Based upon parallax measurements obtained during the Hipparcos mission, it is about 430 light-years distant from the Sun.
| 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 II |
| 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 ± 0.57 mas |
| 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 |
The two components are designated ε Canis Majoris A, officially named Adhara /əˈdɛərə/ – the traditional name of the system, and B.
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