Omicron Cephei
Binary star in the constellation Cepheus
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Omicron Cephei is a binary star system in the northern constellation of Cepheus.[7] 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,[3] 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.
 | |
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Cepheus[1] |
| ο Cep A | |
| Right ascension | 23h 18m 37.493s[2] |
| Declination | +68° 06′ 41.20″[2] |
| Apparent magnitude (V) | 4.86[3] |
| ο Cep B | |
| Right ascension | 23h 18m 37.110s[4] |
| Declination | +68° 06′ 38.64″[4] |
| Apparent magnitude (V) | 7.13[3] |
| Characteristics | |
| U−B color index | +0.49[3] |
| B−V color index | +0.84[3] |
| R−I color index | +0.45[3] |
| ο Cep A | |
| Evolutionary stage | red clump[5] |
| Spectral type | G8III[6] |
| ο Cep B | |
| Evolutionary stage | main sequence[6] |
| Spectral type | F6V[3] |
| Astrometry | |
| ο Cep A | |
| Proper motion (μ) | RA: +54.277 mas/yr[2] Dec.: +9.902 mas/yr[2] |
| Parallax (π) | 16.3251±0.0854 mas[2] |
| Distance | 200 ± 1 ly (61.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 0.78[1] |
| ο Cep B | |
| Proper motion (μ) | RA: +43.343 mas/yr[4] Dec.: +13.343 mas/yr[4] |
| Parallax (π) | 16.3359±0.0485 mas[4] |
| Distance | 199.7 ± 0.6 ly (61.2 ± 0.2 pc) |
| Orbit[6] | |
| 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[6] M☉ |
| Luminosity | 51[1] L☉ |
| Metallicity [Fe/H] | 0.05±0.02[1] dex |
| ο Cep B | |
| Mass | 1.29[6] 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[7][8] | |
| Database references | |
| SIMBAD | data |
| A | |
| B | |
This system consists of a less massive F-type main sequence star in orbit with a more massive G-type giant star.[6] 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.[6]
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.[8][9]