Rho1 Cephei

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Rho1 Cephei
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cepheus
Right ascension 22h 26m 42.40624s[1]
Declination +78° 47′ 09.0725″[1]
Apparent magnitude (V) 5.84[2]
Spectral type A2m[3]
B−V color index −0.16[2]
Proper motion (μ) RA: −13.33[1] mas/yr
Dec.: −36.95[1] mas/yr
Parallax (π) 15.83 ± 0.23[1] mas
Distance 206 ± 3 ly
(63.2 ± 0.9 pc)
ρ1 Cep A
Mass 2.00[3] M
Rotational velocity (v sin i) 81[4] km/s
Age 320[3] Myr
ρ1 Cep B
Mass 0.51[3] M
Other designations
ρ1 Cep, 28 Cep, BD+78° 796, HD 213403, HIP 110787, HR 8578, SAO 10375, WDS J22267+7847AB[5]
Database references

Rho1 Cephei1 Cephei) is a double star located in the northern constellation of Cepheus. As of 2014, the pair had an angular separation of 0.29 arc seconds along a position angle of 211.1°. This corresponds to a projected separation of 18.1 AU.[3] Rho1 Cephei is faintly visible to the naked eye with an apparent visual magnitude of 5.84,[2] and it forms an optical pair with the brighter star Rho2 Cephei. Based upon an annual parallax shift of 15.83 mas as seen from the Earth,[1] Rho1 Cephei is located about 206 light years from the Sun.

The primary component is a chemically peculiar Am star with a stellar classification of A2m.[3] It has twice the mass of the Sun and is around 320 million years old.[3] The smaller companion may be the source of the X-ray emission from this location, as stars similar to the primary component do not generally produce detectable levels of X-rays.[6]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c Oja, T. (August 1991), "UBV photometry of stars whose positions are accurately known. VI", Astronomy and Astrophysics Supplement Series, 89 (2): 415–419, Bibcode:1991A&AS...89..415O. 
  3. ^ a b c d e f g De Rosa, R. J.; et al. (2013), "The VAST Survey - III. The multiplicity of A-type stars within 75 pc", Monthly Notices of the Royal Astronomical Society, 437 (2): 1216, arXiv:1311.7141Freely accessible, Bibcode:2014MNRAS.437.1216D, doi:10.1093/mnras/stt1932. 
  4. ^ Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255Freely accessible, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943. 
  5. ^ "rho01 Cep". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-05-05. 
  6. ^ De Rosa, R. J.; et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society, 415 (1): 854–866, arXiv:1103.4363Freely accessible, Bibcode:2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x.