Rho2 Cephei
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cepheus[1] |
| Right ascension | 22h 29m 52.97797s[2] |
| Declination | +78° 49′ 27.4320″[2] |
| Apparent magnitude (V) | 5.50[3] |
| Characteristics | |
| Evolutionary stage | main sequence[2][4] |
| Spectral type | A3 V[5] |
| U−B color index | +0.07[3] |
| B−V color index | +0.06[3] |
| Astrometry | |
| Radial velocity (Rv) | −1.25±0.37[2] km/s |
| Proper motion (μ) | RA: +3.543 mas/yr[2] Dec.: −20.840 mas/yr[2] |
| Parallax (π) | 13.6037±0.0544 mas[2] |
| Distance | 239.8 ± 1.0 ly (73.5 ± 0.3 pc) |
| Absolute magnitude (MV) | +1.07[1] |
| Details | |
| Mass | 2.26+0.04 −0.11[2] M☉ |
| Radius | 2.43+0.04 −0.02[2] R☉ |
| Luminosity | 36.2+0.8 −5.4[2] L☉ |
| Surface gravity (log g) | 3.60[2] cgs |
| Temperature | 7,405+17 −33[2] K |
| Rotational velocity (v sin i) | 133[6] km/s |
| Age | 85 Myr[7] 503+146 −87[2] Myr |
| Other designations | |
| ρ Cephei, ρ2 Cep, 29 Cephei, BD+78°801, FK5 1593, HD 213798, HIP 111056, HR 8591, SAO 10402[8] | |
| Database references | |
| SIMBAD | data |
Rho2 Cephei is a solitary[9] star in the northern constellation of Cepheus. Its name is a Bayer designation that is Latinized from ρ2 Cephei, or simply ρ Cephei, and abbreviated Rho2 Cep or ρ2 Cep. With an apparent visual magnitude of 5.50,[3] it is faintly visible to the naked eye, forming an optical pair with Rho1 Cephei. Based upon an annual parallax shift of 13.6 mas as seen from the Earth, it is located about 240 light years from the Sun.
Rho2 Cephei is an A-type main sequence star with a stellar classification of A3 V,[5] estimated to be 500 million years old.[2] It has a high rate of rotation, showing a projected rotational velocity of 133 km/s.[6] The star has an estimated 2.26 times the mass of the Sun and 2.43 times the Sun's radius. It is radiating 36 times the luminosity of the Sun from its photosphere at an effective temperature of 7,405 K.[2]
This star has been called by the Arabic name Al Kalb al Rāʽi, the Shepherd's Dog,[10] which is better known (with the spelling Cebalrai) as a name for β Ophiuchi.
References
- ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015 XHIP record for this object at VizieR.
- ^ a b c d e f g h i j k l m n Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875 Gaia DR3 record for this source at VizieR.
- ^ a b c d Oja, T. (April 1983), "UBV photometry of FK4 and FK4 supplement stars", Astronomy and Astrophysics Supplement Series, 52: 131–134, Bibcode:1983A&AS...52..131O.
- ^ Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
- ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
- ^ a b Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
- ^ Gullikson, Kevin; et al. (2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 40, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065.
- ^ "rho Cep", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-05-05.
- ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
- ^ Allen, R. H. (1899), Star Names: Their Lore and Meaning, p. 159, retrieved 2026-02-09