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 37.110s |
| Declination | +68° 06′ 38.64″ |
| 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 | |
| Evolutionary stage | red clump |
| Spectral type | G8III |
| ο Cep B | |
| Evolutionary stage | main sequence |
| Spectral type | F6V |
| Astrometry | |
| ο Cep A | |
| Proper motion (μ) | RA: +54.277 mas/yr Dec.: +9.902 mas/yr |
| Parallax (π) | 16.3251±0.0854 mas |
| Distance | 200 ± 1 ly (61.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.78 |
| ο Cep B | |
| Proper motion (μ) | RA: +43.343 mas/yr Dec.: +13.343 mas/yr |
| Parallax (π) | 16.3359±0.0485 mas |
| Distance | 199.7 ± 0.6 ly (61.2 ± 0.2 pc) |
| Orbit | |
| Period (P) | 1,505±40 years |
| 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) | B1,692±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 | |
| STF 3001AB, ο Cep, Omicron Cephei, Omicron Cep, 34 Cephei, BD+67°1514, GC 32463, HD 219916, HIP 115088, HR 8872, SAO 20554, PPM 24360, ADS 16666 AB, CCDM J23186+6807AB, WDS 23186+6807AB, GSC 04478-01361 | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
Omicron Cephei is a binary star system in the northern constellation of Cepheus. Its name is a Bayer designation that is Latinized from ο Cephei, and abbreviated Omicron Cep or ο Cep. The combined apparent visual magnitude of the system is 4.75, which is bright enough to be visible to the naked eye as a point of light. Based on parallax measurements, it is located at a distance of 200 light-years (61 pc) from Earth.
This system consists of a less massive F-type main sequence star in orbit with a more massive G-type giant star. 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, with a 2003 study giving a period of approximately 1500 years.
There is a visual companion, CCDM J23186+6807C, to the binary star. It has an approximate apparent visual magnitude of 12.8 and is located approximately 45 arcseconds away from it.