Omicron Cephei
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cepheus |
| ο Cep A | |
| Right ascension | 23h 18m 37.493s |
| Declination | +68° 06′ 41.20″ |
| Apparent magnitude (V) | 4.86 |
| ο Cep B | |
| Right ascension | 23h 18m 37.115s |
| Declination | +68° 06′ 38.65″ |
| Apparent magnitude (V) | 7.13 |
| Characteristics | |
| U−B color index | +0.49 |
| B−V color index | +0.84 |
| R−I color index | +0.45 |
| ο Cep A | |
| Spectral type | G8III |
| ο Cep B | |
| Spectral type | F6V |
| Astrometry | |
| ο Cep A | |
| Proper motion (μ) | RA: 54.88 mas/yr Dec.: 10.91 mas/yr |
| Parallax (π) | 15.48±0.55 mas |
| Distance | 211 ± 7 ly (65 ± 2 pc) |
| Absolute magnitude (MV) | 0.78 |
| ο Cep B | |
| Proper motion (μ) | RA: 45.70 mas/yr Dec.: 13.19 mas/yr |
| Orbit | |
| Period (P) | 1505±40 y |
| Semi-major axis (a) | 3.13±0.12 ″ |
| Eccentricity (e) | 0.439±0.020 |
| Inclination (i) | 16.0±4.0° |
| Longitude of the node (Ω) | 4.5±4.5° |
| Periastron epoch (T) | B1692 ± 20 |
| Argument of periastron (ω) (secondary) | 93.0±20.0° |
| Details | |
| ο Cep A | |
| Mass | 2.35 ± 0.15 M☉ |
| Luminosity | 51 L☉ |
| Metallicity [Fe/H] | 0.05±0.02 dex |
| ο Cep B | |
| Mass | 1.29 M☉ |
| Other designations | |
| ο Cep, Omicron Cephei, Omicron Cep, 34 Cephei, 34 Cep, STF 3001AB, ADS 16666 AB, BD+67°1514, CCDM J23186+6807AB, GC 32463, GSC 04478-01361, HD 219916, HIP 115088, HR 8872, IDS 23145+6734 AB, PPM 24360, SAO 20554, WDS 23186+6807AB. | |
| Database references | |
| SIMBAD | data |
Omicron Cephei, Latinized from ο Cephei, is a binary star in the constellation of Cepheus. It consists of a less massive F-type main sequence star in orbit with a more massive G-type giant star. The overall apparent visual magnitude of the system is 4.75.
The pair was first determined to be binary by F. G. W. Struve in 1832. Since then, the secondary has been seen to revolve approximately 45 degrees around the primary. A number of orbits have been computed, the most recent giving a period of approximately 1500 years.