VY Canis Majoris
VY Canis Majoris (abbreviated to VY CMa) is an extreme oxygen-rich (O-rich) red hypergiant (RHG) or red supergiant (RSG) and pulsating variable star 1.2 kiloparsecs (3,900 light-years) from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 22m 58.32877s |
| Declination | −25° 46′ 03.2355″ |
| Apparent magnitude (V) | 6.5–9.6 |
| Characteristics | |
| Evolutionary stage | Red hypergiant |
| Spectral type | M3–M4.5 (M2.5–M5e Ia) |
| Apparent magnitude (U) | 12.01 |
| Apparent magnitude (B) | 10.19 |
| Apparent magnitude (V) | 7.95 |
| Apparent magnitude (J) | 1.98 |
| Apparent magnitude (H) | 0.44 |
| Apparent magnitude (K) | -0.72 |
| U−B color index | +2.32 |
| B−V color index | +2.057 |
| V−R color index | +2.20 |
| Variable type | SRc or Lc |
| Astrometry | |
| Radial velocity (Rv) | 41 km/s |
| Proper motion (μ) | RA: 9.84 mas/yr Dec.: 0.75 mas/yr |
| Parallax (π) | 0.83 ± 0.08 mas |
| Distance | ~3,820+260 −230 ly (1,170+80 −70 pc) |
| Details | |
| Mass | 17±8 M☉ |
| Radius | 1,420±120 R☉ |
| Luminosity | 270,000±40,000, 178,000+40,900 −29,900 L☉ |
| Surface gravity (log g) | −0.6±0.4 cgs |
| Temperature | 3,490±90 K |
| Metallicity [Fe/H] | +0.0 dex |
| Rotational velocity (v sin i) | 300 km/s |
| Age | 8.2 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
No evidence has been found that it is part of a multiple star system. Its great infrared (IR) excess makes it one of the brightest objects in the local part of the galaxy at wavelengths of 5 to 20 microns (µm) and indicates a dust shell or heated disk. It is about 17±8 times the mass of the Sun (M☉). It is surrounded by a complex asymmetric circumstellar envelope (CSE) caused by its mass loss. It produces strong molecular maser emission and was one of the first radio masers discovered. VY CMa is embedded in the large molecular cloud Sh2-310, a large, quite local star-forming H II region—its diameter: 480 arcminutes (′) or 681 ly (209 pc).
The radius of VY CMa is very roughly 1,420 times that of the Sun (R☉), which is close to the modelled maximum, the Hayashi limit, a volume nearly 3 billion times that of the Sun. Taking this mid-point estimate as correct, an object travelling at the speed of light would take 6 hours to go around its surface, compared to 14.5 seconds for the Sun. If this star replaced the Sun its surface would, per this approximation, be beyond the orbit of Jupiter.