Eta Canis Majoris
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 24m 05.70228s |
| Declination | −29° 18′ 11.1798″ |
| Apparent magnitude (V) | 2.38 – 2.48 |
| Characteristics | |
| Evolutionary stage | Blue supergiant, likely a post-red supergiant |
| Spectral type | B5 Ia |
| U−B color index | −0.708 |
| B−V color index | −0.087 |
| Variable type | α Cyg |
| Astrometry | |
| Radial velocity (Rv) | 41.1 km/s |
| Proper motion (μ) | RA: −4.14 mas/yr Dec.: 5.81 mas/yr |
| Parallax (π) | 1.64±0.40 mas |
| Distance | approx. 2,000 ly (approx. 600 pc) |
| Absolute magnitude (MV) | −7.0 |
| Details | |
| Mass | 5.5 or 9.5 M☉ |
| Radius | 54 R☉ |
| Luminosity | 163,800+4,200 −15,900 L☉ |
| Surface gravity (log g) | 1.95+0.02 −0.03 cgs |
| Temperature | 15,800+100 −400 K |
| Rotational velocity (v sin i) | 51.5±5.0 km/s |
| Age | 8.3 Myr |
| Other designations | |
| Aludra, 31 Canis Majoris, CD−29°4328, FK5 283, HD 58350, HIP 35904, HR 2827, SAO 173651 | |
| Database references | |
| SIMBAD | data |
Eta Canis Majoris (η Canis Majoris, abbreviated Eta CMa, η CMa), also named Aludra /əˈluːdrə, əˈljuːdrə/, is a blue supergiant star in the constellation of Canis Major. It has an apparent magnitude varying between 2.38 and 2.48, which makes it the fifth-brightest in the constellation and brightest stars. Parallax measurements from the Hipparcos mission give a large distance of 2,000 light-years.