W Canis Majoris
Star in the constellation Canis Major
From Wikipedia, the free encyclopedia
W Canis Majoris (W CMa) is a carbon star in the constellation Canis Major. A cool star, it has a surface temperature of around 2,900 K[4] and a radius 234 times that of the Sun,[9] with a bolometric absolute magnitude of −4.13 and distance estimated at 443 or 445 parsecs (1,444–1,450 light-years) based on bolometric magnitude or radius. The Gaia Data Release 2 parallax of 1.8049±0.1454 milliarcseconds implies a distance of about 555 parsecs. It is a variable star, whose brightness ranges from magnitude 6.35 to 7.90. At its brightest, it might be very faintly visible to the naked eye of an observer with ideal observing conditions.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 08m 03.43652s[2] |
| Declination | −11° 55′ 23.7977″[2] |
| Apparent magnitude (V) | 6.35–7.90[3] |
| Characteristics | |
| Evolutionary stage | AGB[4] |
| Spectral type | C6,3(N)[3] |
| B−V color index | +2.55[5] |
| Variable type | Lb[3][6] |
| Astrometry | |
| Radial velocity (Rv) | 23.00[7] km/s |
| Proper motion (μ) | RA: −6.518[2] mas/yr Dec.: 2.280[2] mas/yr |
| Parallax (π) | 1.8049±0.1454 mas[8] |
| Distance | 1,800 ± 100 ly (550 ± 40 pc) |
| Details | |
| Radius | 234[9] R☉ |
| Luminosity | 2,900[4] L☉ |
| Surface gravity (log g) | 0.0[9] cgs |
| Temperature | 2,900[9][4] K |
| Other designations | |
| W CMa, BD−11°1805, HIP 34413, HD 54361, SAO 152427 | |
| Database references | |
| SIMBAD | data |
Variability
In 1901, it was announced that Williamina Fleming had discovered the star, then called BD −11° 1805, is a variable star.[10] It was given its variable star designation, W Canis Majoris, in 1912.[11] W CMa is classified as a slow irregular variable star. Detailed analyses have found only very weak and probably spurious periods of approximately a month.[6] It is a carbon star, an asymptotic giant branch star where carbon and s-process elements have been dredged up to the surface during thermal pulses of the helium-burning shell.[12]