Nu Andromedae

Not to be confused with Andromeda V or 5 Andromedae. "ν And" redirects here. For other uses, see Vand.

Nu Andromedae is a binary star system in the constellation Andromeda. Its Bayer designation is Latinized from ν Andromedae, and abbreviated Nu And or ν And, respectively. The system has an apparent visual magnitude of 4.5,^[2] which is bright enough to be seen with the naked eye. Based on parallax measurements, it is located at a distance of approximately 560 light-years (170 parsecs) from Earth.^[1] The pair are drifting closer with a heliocentric radial velocity of –24 km/s.^[6] Situated just over a degree to the west of this star is the Andromeda Galaxy.^[12]

Nu Andromedae is the prominent blue star in the upper right of this image. At the center is the Andromeda Galaxy.

Nu Andromedae

Location of ν Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	00h 49m 48.846s[1]
Declination	+41° 04′ 44.08″[1]
Apparent magnitude (V)	4.522[2]
Characteristics
Spectral type	B4/5 V[3][4] + F8 V[5]
U−B color index	–0.573[2]
B−V color index	–0.136[2]
Astrometry
Radial velocity (Rv)	–23.9[6] km/s
Proper motion (μ)	RA: +21.711 mas/yr[1] Dec.: –18.694 mas/yr[1]
Parallax (π)	5.7868±0.1857 mas[1]
Distance	560 ± 20 ly (173 ± 6 pc)
Absolute magnitude (MV)	−1.85[7]
Orbit[5]
Period (P)	4.2827 d
Eccentricity (e)	0.03
Longitude of the node (Ω)	25.°
Periastron epoch (T)	18,155.67
Semi-amplitude (K1) (primary)	71.7 km/s
Semi-amplitude (K2) (secondary)	101.9 km/s
Details
ν And A
Mass	5.9±0.2[3] M☉
Radius	3.4[8] R☉
Luminosity	1,104[7] L☉
Surface gravity (log g)	4.12±0.43[9] cgs
Temperature	14,851±396[9] K
Metallicity [Fe/H]	+0.14±0.17[9] dex
Rotational velocity (v sin i)	20[10] km/s
Age	63.1±17.9[3] Myr
Other designations
ν Andromedae, ν And, Nu And, 35 Andromedae, 35 And, BD+40 171, FK5 1021, HD 4727, HIP 3881, HR 226, SAO 36699, PPM 43365[11]
Database references
SIMBAD	data

Nu Andromedae is close spectroscopic binary^[3] system with a period of 4.2828 days and a nearly circular orbit.^[5] The primary component is a B-type main sequence star with a stellar classification of B5 V.^[3] The fainter secondary has a classification of F8 V,^[5] which makes it an F-type main sequence star. The pair is about 63 million years old.^[3]

The pair have a peculiar velocity of 22.16±0.87 km/s relative to neighboring stars, which doesn't qualify it to be a runaway star system but does suggest it escaped its star cluster of origin. The trajectory indicates it may have left the NGC 6405 cluster some 25 million years ago.^[13]

Naming

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ν Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, π 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 ν Andromedae itself is 奎宿七 (Kuí Sù qī, English: the Seventh Star of Legs.)^[14]