2 Persei

2 Persei is a binary star system in the northern constellation Perseus, located around 500 light years away from the Sun. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude is 5.70.^[2] The system is moving further away from the Earth with a heliocentric radial velocity of 11 km/s.^[4]

2 Persei

Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	01h 52m 09.3723s[1]
Declination	+50° 47′ 34.054″[1]
Apparent magnitude (V)	5.70[2]
Characteristics
Spectral type	B9pHgMn[3]
B−V color index	−0.067±0.004[2]
Astrometry
Radial velocity (Rv)	11.4±0.2[4] km/s
Proper motion (μ)	RA: +17.532[1] mas/yr Dec.: −29.090[1] mas/yr
Parallax (π)	6.8219±0.1092 mas[1]
Distance	478 ± 8 ly (147 ± 2 pc)
Absolute magnitude (MV)	−0.14[2]
Orbit[4]
Primary	2 Persei A
Companion	2 Persei B
Period (P)	5.62698±0.00002 d
Eccentricity (e)	0.024±0.011
Periastron epoch (T)	2440281.3±0.4 JD
Argument of periastron (ω) (primary)	208±24°
Semi-amplitude (K1) (primary)	26.5±0.3 km/s
Details
Mass	3.2[1] M☉
Radius	3.7[1] R☉
Luminosity	156[1] L☉
Surface gravity (log g)	3.74[1] cgs
Temperature	11,218[1] K
Metallicity [Fe/H]	−0.74[1] dex
Rotational velocity (v sin i)	25[5] km/s
Age	233[1] Myr
Other designations
BD+50°379, FK5 1052, HD 11291, HIP 8714, HR 536, SAO 22696[6]
Database references
SIMBAD	data

In 1970 radial velocity measurements from spectrograms taken at David Dunlap Observatory indicated it was a single-lined spectroscopic binary.^[7][5] Follow up observations led to the determination that it had a nearly circular orbit with a period of 5.6 days.^[4] The visible component is a chemically peculiar mercury-manganese star with a stellar classification of B9pHgMn.^[3] Other analyses of its spectrum have assigned it the giant star spectral type of B9III.^[8]