Pi Andromedae

Pi Andromedae is a binary star^[3] system in the northern constellation of Andromeda. Its Bayer designation is latinized from π Andromedae, and abbreviated Pi And or π And, respectively. With an apparent visual magnitude of 4.4,^[2] it is visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 580 light-years (180 parsecs) from Earth.^[1]

Pi Andromedae

Location of π Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	00h 36m 52.85132s[1]
Declination	+33° 43′ 09.6363″[1]
Apparent magnitude (V)	4.36[2] (4.9/5.3)[3]
Characteristics
Spectral type	B5 V[4] (B5 V + B5 V[3])
U−B color index	–0.55[2]
B−V color index	–0.16[2]
Astrometry
Radial velocity (Rv)	+8.7[5] km/s
Proper motion (μ)	RA: 14.669(118) mas/yr[1] Dec.: −3.385(93) mas/yr[1]
Parallax (π)	5.6563±0.1474 mas[1]
Distance	580 ± 20 ly (177 ± 5 pc)
Orbit[6]
Period (P)	143.53±0.06 d
Semi-major axis (a)	6.69±0.05 mas
Eccentricity (e)	0.542±0.006
Inclination (i)	103.0±0.2°
Longitude of the node (Ω)	94.7±0.2°
Periastron epoch (T)	7717.7±0.4
Argument of periastron (ω) (secondary)	170.7±0.7°
Semi-amplitude (K1) (primary)	47.50±0.53 km/s
Semi-amplitude (K2) (secondary)	117.4±2.8 km/s
Details[7]
A
Mass	5.8[6] M☉
Radius	4.7 R☉
Luminosity	1,000 L☉
Surface gravity (log g)	4.10[4] cgs
Temperature	15,000 K
Metallicity [Fe/H]	–0.20[4] dex
Rotational velocity (v sin i)	25[8] km/s
Age	80 Myr
B
Mass	4.8[6] M☉
Radius	4.7 R☉
Luminosity	1,000 L☉
Temperature	15,000 K
Other designations
Pi And, π Andromedae, π And, 29 Andromedae, BD+32°101, FK5 18, HD 3369, HIP 2912, HR 154, SAO 54033, PPM 65480, ADS 513
Database references
SIMBAD	data

π Andromedae in optical light

The pair is classified as a blue-white B-type main sequence dwarf, with an apparent magnitude of +4.34. It is a spectroscopic binary with an orbital period of 143.5 days and an eccentricity of 0.54.^[6]

The spectroscopic binary forms a triple system with BD+32 102, a magnitude 8.6 star located 35.9 arcseconds away.^[3] At 55 arcseconds separation is an 11th magnitude companion that is just located on the same line of sight, but at a very different distance from us.

Naming

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of π Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, τ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for π Andromedae itself is 奎宿六 (Kuí Sù liù, English: the Sixth Star of Legs.)^[9]