Delta Cephei
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| δ Cep A | |
| Right ascension | 22h 29m 10.26502s |
| Declination | +58° 24′ 54.7139″ |
| Apparent magnitude (V) | 4.07 (3.48–4.37) / 7.5 |
| δ Cep C | |
| Right ascension | 22h 29m 09.248s |
| Declination | +58° 24′ 14.76″ |
| Apparent magnitude (V) | 6.3 |
| Characteristics | |
| Spectral type | F5Ib-G1Ib + B7-8 |
| U−B color index | 0.36 |
| B−V color index | 0.60 |
| Variable type | Cepheid |
| Astrometry | |
| Radial velocity (Rv) | −16.8 km/s |
| Proper motion (μ) | RA: +15.35 mas/yr Dec.: +3.52 mas/yr |
| Parallax (π) | 3.66±0.10 mas |
| Distance | 890 ± 20 ly (273 ± 7 pc) |
| Absolute magnitude (MV) | −3.47±0.10 (−3.94 to −3.05) |
| Orbit | |
| Primary | δ Cep A |
| Name | δ Cep B |
| Period (P) | 9.32+0.03 −0.04 years |
| Semi-major axis (a) | 0.029+0.002 −0.003″ |
| Eccentricity (e) | 0.71±0.02 |
| Inclination (i) | 124+17 −12° |
| Longitude of the node (Ω) | 78+56 −50° |
| Periastron epoch (T) | 1982.294+0.111 −0.101 |
| Argument of periastron (ω) (secondary) | 230+4 −3° |
| Semi-amplitude (K1) (primary) | 1.509±0.2 km/s |
| Details | |
| δ Cep A | |
| Mass | 5.26+1.26 −1.4 M☉ |
| Radius | 46.1+1.9 −2.1 R☉ |
| Luminosity | 1,949±107 L☉ |
| Surface gravity (log g) | 1.65 cgs |
| Temperature | 5,905±29 K |
| Metallicity [Fe/H] | +0.08 dex |
| Rotational velocity (v sin i) | 9 km/s |
| δ Cep B | |
| Mass | 0.72±0.11 M☉ |
| δ Cep C | |
| Temperature | 8,800 K |
| Other designations | |
| 27 Cephei, BD+57 2548, FK5 847, HD 213306, HIP 110991, HR 8571, SAO 34508 | |
| Database references | |
| SIMBAD | data |
Delta Cephei is a quadruple star system in the northern constellation of Cepheus, the King. Its name is a Bayer designation that is Latinized from δ Cephei, and abbreviated Delta Cep or δ Cep. Based on parallax measurements, it is located approximately 890 light-years away from Earth. At this distance, the visual magnitude of the star is diminished by 0.23 as a result of extinction caused by gas and dust along the line of sight. It is the prototype of the Cepheid variable stars that undergo periodic changes in luminosity.