Cygnus OB2-12
Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude (all electromagnetic radiation) of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 32m 40.9572s |
| Declination | 41° 14′ 29.279″ |
| Apparent magnitude (V) | 11.702 |
| Characteristics | |
| Spectral type | B3–4 Ia+ |
| Apparent magnitude (B) | 14.41 |
| Apparent magnitude (V) | 11.40 |
| Apparent magnitude (J) | 4.667±0.324 |
| Apparent magnitude (H) | 3.512±0.260 |
| Apparent magnitude (K) | 2.704±0.364 |
| U−B color index | 1.69 |
| B−V color index | 3.01 |
| Variable type | cLBV |
| Astrometry | |
| Radial velocity (Rv) | −11.00 km/s |
| Proper motion (μ) | RA: −1.703 mas/yr Dec.: −3.412 mas/yr |
| Parallax (π) | 0.5895 ± 0.0518 mas |
| Distance | 5,500 ± 500 ly (1,700 ± 100 pc) |
| Absolute magnitude (MV) | −9.82 |
| Details | |
| Mass | 110 M☉ |
| Radius | 246 R☉ |
| Luminosity | 1,660,000 L☉ |
| Temperature | 13,700 K |
| Age | 3.0 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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