Epsilon Canis Majoris
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Canis Major |
| ε CMa A | |
| Right ascension | 06h 58m 37.54876s |
| Declination | −28° 58′ 19.5102″ |
| Apparent magnitude (V) | 1.50 |
| ε CMa B | |
| Right ascension | 06h 58m 37.73467s |
| Declination | −28° 58′ 26.8595″ |
| Apparent magnitude (V) | +7.5 |
| Characteristics | |
| ε CMa A | |
| Evolutionary stage | Blue giant, main sequence or stellar merger product |
| Spectral type | B2 II or B2 III-II |
| U−B color index | −0.93 |
| B−V color index | −0.21 |
| Astrometry | |
| ε CMa A | |
| Radial velocity (Rv) | +27.3±0.4 km/s |
| Proper motion (μ) | RA: +3.24 mas/yr Dec.: +1.33 mas/yr |
| Parallax (π) | 8.05±0.14 mas |
| Distance | 405 ± 7 ly (124 ± 2 pc) |
| Absolute magnitude (MV) | −3.97±0.04 |
| ε CMa B | |
| Radial velocity (Rv) | +28.46±2.20 km/s |
| Proper motion (μ) | RA: +1.802 mas/yr Dec.: −0.610 mas/yr |
| Parallax (π) | 7.6159 ± 0.0223 mas |
| Distance | 428 ± 1 ly (131.3 ± 0.4 pc) |
| Position (relative to A) | |
| Component | B |
| Epoch of observation | 2008 |
| Angular distance | 7.90″ |
| Position angle | 162° |
| Details | |
| ε CMa A | |
| Mass | 13.1±2.3 M☉ |
| Radius | 10.7±0.7 R☉ |
| Luminosity | 19,900±1,600 L☉ 22,400+2,700 −2,400 L☉ |
| Surface gravity (log g) | 3.50±0.05 cgs |
| Temperature | 22,500±300 K |
| Rotation | 5 days |
| Rotational velocity (v sin i) | 25 km/s |
| Age | 17.5 – 19 Myr |
| ε CMa B | |
| Mass | 1.54 M☉ |
| Radius | 1.54 R☉ |
| Luminosity | 6.13 L☉ |
| Surface gravity (log g) | 4.15 cgs |
| Temperature | 7,315 K |
| Other designations | |
| Adhara, Adharaz, Undara, ε CMa, 21 CMa, CD−28°3666, FK5 268, HD 52089, HIP 33579, HR 2618, SAO 172676, ADS 5654 | |
| Database references | |
| ε CMa A | |
| SIMBAD | data |
| ε CMa B | |
| SIMBAD | data |
Epsilon Canis Majoris is a binary star system and the second-brightest star 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 and the Gaia mission, it is about 405–428 light-years distant.
The two components are designated ε Canis Majoris A, officially named Adhara /əˈdɛərə/ – the traditional name of the system, and B.