Delta Cephei
Delta Cephei (δ Cep, δ Cephei) is a quadruple star system located approximately 887 light-years away in the northern constellation of Cepheus, the King. 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.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| 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) | 3.77 ± 0.16 mas |
| Distance | 887 ± 26 ly (272 ± 8 pc) |
| Absolute magnitude (MV) | –3.47 ± 0.10 (–3.94 - –3.05) |
| Details | |
| δ Cep A | |
| Mass | 4.5 ± 0.3 M☉ |
| Radius | 44.5 R☉ |
| Luminosity | ~2000 L☉ |
| Temperature | 5,500–6,800 K |
| Metallicity [Fe/H] | +0.08 dex |
| Rotational velocity (v sin i) | 9 km/s |
| Age | ~100 Myr |
| δ Cep B | |
| Mass | 0.2 - 1.2 M☉ |
| Orbit | |
| Primary | δ Cep A |
| Companion | δ Cep B |
| Period (P) | 6.03 yr |
| Eccentricity (e) | 0.647 |
| Semi-amplitude (K1) (primary) | 1.509 ± 0.2 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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