Alpha Cephei
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 21h 18m 34.7723s |
| Declination | +62° 35′ 08.069″ |
| Apparent magnitude (V) | 2.46 |
| Characteristics | |
| Spectral type | A8Vn or A7IV-V |
| U−B color index | +0.12 |
| B−V color index | +0.21 |
| Variable type | suspected δ Sct |
| Astrometry | |
| Radial velocity (Rv) | −15.8±1.1 km/s |
| Proper motion (μ) | RA: +150.55 mas/yr Dec.: 49.09 mas/yr |
| Parallax (π) | 66.50±0.11 mas |
| Distance | 49.05 ± 0.08 ly (15.04 ± 0.02 pc) |
| Absolute magnitude (MV) | 1.57 |
| Details | |
| Mass | 2.00±0.15 M☉ |
| Radius | 2.175±0.046 (polar) 2.823±0.097 (equator) R☉ |
| Luminosity | 17 L☉ |
| Surface gravity (log g) | 3.99 cgs |
| Temperature | 8,440+430 −700 (polar) 7,600 (equator) K |
| Metallicity [Fe/H] | 0.09 dex |
| Rotation | 12.11±0.26 h |
| Rotational velocity (v sin i) | 283±19 km/s |
| Age | 820 Myr |
| Other designations | |
| Alderamin, α Cep, 5 Cep, AG+62°1226, BD+61°2111, FK5 803, GJ 826, HD 203280, HIP 105199, HR 8162, SAO 19302, CCDM J21186+6236A, 2MASS J21183475+6235081 | |
| Database references | |
| SIMBAD | data |
Alpha Cephei (α Cephei, abbreviated Alpha Cep, α Cep), officially named Alderamin /ælˈdɛrəmɪn/, is a second magnitude star in the constellation of Cepheus near the northern pole. The star is relatively close to Earth at 49 light years (ly) and drifting closer with a heliocentric radial velocity of about −16 km/s.