Rho1 Cephei

Rho¹ Cephei (ρ¹ 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.

For other stars with this Bayer designation, see ρ Cephei.

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]
Characteristics
Spectral type	A2m[3]
B−V color index	−0.16[2]
Astrometry
Proper motion (μ)	RA: −13.33[1] mas/yr Dec.: −36.95[1] mas/yr
Parallax (π)	15.83±0.23 mas[1]
Distance	206 ± 3 ly (63.2 ± 0.9 pc)
Details
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
SIMBAD	data

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]