| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 23h 07m 53.854s[1] |
| Declination | +75° 23′ 15.00″[1] |
| Apparent magnitude (V) | 4.419[2]4.61[3] + 6.75[4]) |
| Characteristics | |
| Spectral type | G7III[5] / F5V[5] / A7V-A9V[6] |
| U−Bcolor index | -0.46 |
| B−Vcolor index | 0.8 |
| Astrometry | |
| Radial velocity (Rv) | -18.6 ± 0.9 km/s |
| Proper motion (μ) | RA: 6.81 ± 1.05[1]mas/yr Dec.: -34.06 ± 0.88[1]mas/yr |
| Parallax (π) | 13.8±0.41 mas[6] |
| Distance | 236 ± 7 ly (72 ± 2 pc) |
| Absolute magnitude (MV) | 0.24 |
| Orbit[5] | |
| Primary | π Cep Aa |
| Companion | π Cep Ab |
| Period (P) | 556.72 ± 0.05 d |
| Semi-major axis (a) | 39.0 ± 3.9mas[6] |
| Eccentricity (e) | 0.297 ± 0.006 |
| Inclination (i) | 99.0 ± 2.5[6]° |
| Longitude of the node (Ω) | 109.2 ± 3.5[6]° |
| Periastronepoch (T) | 2,439,172.9 ± 1.6 |
| Argument of periastron (ω) (secondary) | 7.6 ± 1.2° |
| Semi-amplitude (K1) (primary) | 24.18 ± 0.15 km/s |
| Orbit[7] | |
| Primary | π Cephei A (Aa + Ab) |
| Companion | π Cephei B |
| Period (P) | 162.8 ± 2.8yr |
| Semi-major axis (a) | 0.810 ± 0.050″ |
| Eccentricity (e) | 0.5968 ± 0.0067 |
| Inclination (i) | 30.0 ± 3.0° |
| Longitude of the node (Ω) | 90.3 ± 4.9° |
| Periastronepoch (T) | B 1934.573 ± 0.35 |
| Argument of periastron (ω) (secondary) | 90.0 ± 4.4° |
| Details[6] | |
| π Cep Aa | |
| Mass | 3.63 ± 0.53 M☉ |
| Surface gravity (log g) | 3.05±0.11[8] cgs |
| Temperature | 5,226±92[8] K |
| Metallicity [Fe/H] | 0.29±0.05[8] dex |
| Age | 100[8] Myr |
| π Cep Ab | |
| Mass | 3.27 ± 0.48 M☉ |
| π Cep B | |
| Mass | 1.93 ± 0.23 M☉ |
| Other designations | |
| HD 218658,HR 8819,33 Cephei,BD+74° 1006,SAO 10629,HIP 114222[9] | |
| Database references | |
| SIMBAD | data |
Pi Cephei (π Cephei) is atrinary star located in the constellationCepheus.[6] With a combinedapparent magnitude of about 4.4,[2] the system is faintly visible to the naked eye. The inner pair of stars orbits in 1.5 years while the outer companion completes one orbit in about 160 years.[6]
Pi Cephei was found to have a visual companion star byOtto Wilhelm von Struve in 1843.[6] That the primary is itself aspectroscopic binary was first noticed byWilliam Wallace Campbell in 1901 usingphotographic plates taken atLick Observatory.[10]
