Epsilon Andromedae

Epsilon Andromedae is a star in the constellation of Andromeda.^[5] Its identifier is a Bayer designation that is Latinized from ε Andromedae, and abbreviated eps And or ε And, respectively. This star can be seen with the naked eye, having an apparent visual magnitude of 4.4.^[2] Based upon an annual parallax shift of 19.2 mas as seen from Earth,^[1] it is located approximately 169 light years from the Sun. The system is moving closer to the Sun with a radial velocity of −84 km/s.^[7] Its orbit in the Milky Way is highly eccentric, causing it to move rapidly relative to the Sun and its neighboring stars.^[9]

ε Andromedae

Location of ε Andromedae (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Andromeda
Right ascension	00h 38m 33.347s[1]
Declination	+29° 18′ 42.31″[1]
Apparent magnitude (V)	4.357[2]
Characteristics
Evolutionary stage	red clump[3]
Spectral type	G6 III Fe−3 CH1[4]
U−B color index	+0.463[2]
B−V color index	+0.8713[2]
V−R color index	+0.6[5]
R−I color index	+0.51[6]
Astrometry
Radial velocity (Rv)	−84.43±0.15[7] km/s
Proper motion (μ)	RA: −228.701 mas/yr[1] Dec.: −253.206 mas/yr[1]
Parallax (π)	19.2451±0.1188 mas[1]
Distance	169 ± 1 ly (52.0 ± 0.3 pc)
Absolute magnitude (MV)	+0.69[8]
Details[7]
Mass	1.01±0.35 M☉
Radius	9.04±0.34 R☉
Luminosity	51.3 L☉
Surface gravity (log g)	2.88±0.02 cgs
Temperature	5,082±20 K
Metallicity [Fe/H]	−0.53±0.05 dex
Rotational velocity (v sin i)	1.70±0.45 km/s
Age	5.71±5.29 Gyr
Other designations
ε And, eps And, 30 Andromedae, BD+28°103, FK5 19, GC 759, HD 3546, HIP 3031, HR 163, SAO 74164, PPM 90002, LTT 10215, NLTT 2065[5]
Database references
SIMBAD	data

This is an evolved G-type giant star with a stellar classification of G6 III Fe−3 CH1.^[4] The suffix notation indicates there is a strong underabundance of iron in the spectrum, and an overabundance of cyanogen (CN). ε Andromedae is believed to be a red clump^[3] star which is fusing helium in its core. It has about the same mass as the Sun, but has expanded to nine times the Sun's radius. The star is radiating 51 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,082 K.^[7]

Naming

In Chinese, 奎宿 (Kuí Sù), meaning Legs (asterism), refers to an asterism consisting of ε Andromedae, η Andromedae, 65 Piscium, ζ Andromedae, δ Andromedae, π 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 ε Andromedae itself is 奎宿四 (Kuí Sù sì, English: the Fourth Star of Legs.)^[10]