| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cepheus |
| Right ascension | 23 07 53.854 |
| Declination | +75° 23′ 15.00″ |
| Apparent magnitude (V) | 4.419 4.61 + 6.75) |
| Characteristics | |
| Spectral type | G7III / F5V / A7V-A9V |
| U−B color index | -0.46 |
| B−V color index | 0.8 |
| Astrometry | |
| Radial velocity (Rv) | -18.6 ± 0.9 km/s |
| Proper motion (μ) | RA: 6.81 ± 1.05 mas/yr Dec.: -34.06 ± 0.88 mas/yr |
| Parallax (π) | 13.8 ± 0.41 mas |
| Distance | 236 ± 7 ly (72 ± 2 pc) |
| Absolute magnitude (MV) | 0.24 |
| Orbit | |
| Primary | π Cep Aa |
| Companion | π Cep Ab |
| Period (P) | 556.72 ± 0.05 d |
| Semi-major axis (a) | 39.0 ± 3.9 mas |
| Eccentricity (e) | 0.297 ± 0.006 |
| Inclination (i) | 99.0 ± 2.5° |
| Longitude of the node (Ω) | 109.2 ± 3.5° |
| Periastron epoch (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 | |
| Primary | π Cephei A (Aa + Ab) |
| Companion | π Cephei B |
| Period (P) | 162.8 ± 2.8 yr |
| 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° |
| Periastron epoch (T) | B 1934.573 ± 0.35 |
| Argument of periastron (ω) (secondary) | 90.0 ± 4.4° |
| Details | |
| π Cep Aa | |
| Mass | 3.63 ± 0.53 M☉ |
| Surface gravity (log g) | 3.05±0.11 cgs |
| Temperature | 5,226±92 K |
| Metallicity | 0.29±0.05 dex |
| Age | 100 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 | |
| Database references | |
| SIMBAD | data |
Pi Cephei (π Cephei) is a trinary star located in the constellation Cepheus. With a combined apparent magnitude of about 4.4, 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.
Pi Cephei was found to have a visual companion star by Otto Wilhelm von Struve in 1843. That the primary is itself a spectroscopic binary was first noticed by William Wallace Campbell in 1901 using photographic plates taken at Lick Observatory.
References
- ^ van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
- ^ Hauck, B.; Mermilliod, M. (1998). "Uvbybeta photoelectric photometric catalogue". Astronomy and Astrophysics Supplement. 129 (3): 431–433. Bibcode:1998A&AS..129..431H. doi:10.1051/aas:1998195.Vizier catalog entry
- Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
- Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (2002). "The Tycho double star catalogue". Astronomy and Astrophysics. 384: 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822.
- ^ Scarfe, C. D.; et al. (1983). "Revised orbits for 105 Herculis and Pi Cephei A and a model for the Pi Cephei system". Monthly Notices of the Royal Astronomical Society. 203: 103–116. Bibcode:1983MNRAS.203..103S. doi:10.1093/mnras/203.1.103.
- ^ Gatewood, George; et al. (2001). "Hipparcos and MAP Studies of the Triple Star π Cephei". The Astrophysical Journal. 549 (2): 1145–1150. Bibcode:2001ApJ...549.1145G. doi:10.1086/319458.
- "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 3 June 2017.
- ^ Feuillet, Diane K.; Bovy, Jo; Holtzman, Jon; Girardi, Léo; MacDonald, Nick; Majewski, Steven R.; Nidever, David L. (2016). "Determining Ages of APOGEE Giants with Known Distances". The Astrophysical Journal. 817 (1): 40. arXiv:1511.04088. Bibcode:2016ApJ...817...40F. doi:10.3847/0004-637X/817/1/40. S2CID 118675933.
- "* pi. Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2013-09-01.
- Campbell, William Wallace (1901). "Some recent results secured with the Mills spectrograph". Lick Observatory Bulletin. 1 (4): 22–25. Bibcode:1901LicOB...1...22C. doi:10.5479/ADS/bib/1901LicOB.1.22C.
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