57 Geminorum

This article is about A Geminorum and is not to be confused with α (alpha) Geminorum.

57 Geminorum (57 Gem) is a yellow giant star in the constellation Gemini, with an apparent magnitude of 5.0. At a distance of about 179 light years, it has a luminosity about 29 times the Sun's. With an age of about 1.2 billion years, it has evolved away from the main sequence and expanded to seven times the width of the Sun.

57 Geminorum

Location of 57 Geminorum (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Gemini
Right ascension	07h 23m 28.511s[1]
Declination	+25° 03′ 01.91″[1]
Apparent magnitude (V)	5.018[2]
Characteristics
Spectral type	G8III[3]
U−B color index	+1.778[2]
B−V color index	+0.174[2]
Astrometry
Radial velocity (Rv)	5.43±0.13[1] km/s
Proper motion (μ)	RA: −66.676[1] mas/yr Dec.: −29.082[1] mas/yr
Parallax (π)	18.1774±0.1459 mas[1]
Distance	179 ± 1 ly (55.0 ± 0.4 pc)
Absolute magnitude (MV)	1.66[4]
Details
Mass	2.2[5] M☉
Radius	7.1[1] R☉
Luminosity	29[1] L☉
Surface gravity (log g)	2.84[4] cgs
Temperature	4,902[4] K
Metallicity [Fe/H]	0.21[4] dex
Rotational velocity (v sin i)	1.3[6] km/s
Age	1.2[7] Gyr
Other designations
A Geminorum, 57 Gem, HR 2808, HD 57727, BD+25°1660, HIP 35846, SAO 79352
Database references
SIMBAD	data

57 Geminorum is the star's Flamsteed designation. It also has the rarely-used Bayer designation A Geminorum.

The radial velocity of 57 Geminorum has been closely examined for indications that it may have orbiting exoplanets, but it shows a particularly stable radial velocity.^[8][9]