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Cygnus OB2-12 as seen by a hypothetical close orbiting planet. |
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| Observation data Epoch J2000 Equinox J2000 |
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|---|---|
| Constellation | Cygnus |
| Right ascension | 20h 32m 40.9589s |
| Declination | 41° 14′ 29.286″ |
| Characteristics | |
| Spectral type | B3-B5Iae |
| 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 |
| B−V color index | 3.0 |
| Astrometry | |
| Proper motion (μ) | RA: 1.91 mas/yr Dec.: -2.47 mas/yr |
| Parallax (π) | -0.60 ± 2.07 mas |
| Distance | approx. -5000 ly (approx. -2000 pc) |
| Absolute magnitude (MV) | -10.6 |
| Details | |
| Mass | 92 M☉ |
| Radius | 244 R☉ |
| Luminosity | 6,300,000 L☉ |
| Temperature | 18,500 K |
| Age | 6.43 million years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Cygnus OB2-12 is an extremely bright blue hypergiant with an absolute bolometric magnitude (all electromagnetic radiation) of -12.2, which approaches the upper limit believed possible for normal single stars. This makes the star more than 6 million times brighter than the Sun, and among the most luminous stars known in the galaxy.
It is a member of the Cyg OB2 Association, a cluster of young massive stars about 5000 light years away in Cygnus, and resides in a region of the Galaxy from which visible light is heavily absorbed by interstellar dust when viewed from the Earth. Were it not for the dust extinction, the star would have a visual magnitude about 1.5, nearly as bright as Deneb (Alpha Cygni), but because of the dust, the observed visual magnitude is 11.4, so that it requires binoculars or a small telescope to be seen.
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