Upsilon Geminorum

Not to be confused with U Geminorum.

Upsilon Geminorum, Latinized from υ Geminorum, is a star in the constellation Gemini. It has an apparent visual magnitude of 4.04,^[2] which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 12.88 mas,^[1] it is around 253 light years from the Sun. There is a visual companion: a magnitude 13.20 star located at an angular separation of 55.20″ along a position angle of 40°, as of 2008.^[10]

υ Geminorum

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Gemini
Right ascension	07h 35m 55.35001s[1]
Declination	+26° 53′ 44.6802″[1]
Apparent magnitude (V)	4.04[2] (4.04 - 4.08[3])
Characteristics
Spectral type	M0 III[4]
U−B color index	+1.96[2]
B−V color index	+1.54[2]
Variable type	suspected[3]
Astrometry
Radial velocity (Rv)	−21.61±0.19[5] km/s
Proper motion (μ)	RA: −32.841 mas/yr[1] Dec.: −106.002 mas/yr[1]
Parallax (π)	12.8761±0.2288 mas[1]
Distance	253 ± 5 ly (78 ± 1 pc)
Absolute magnitude (MV)	−0.53[6]
Details
Mass	1.52[7] M☉
Radius	39.62+0.74 −0.76[8] R☉
Luminosity	369.6±18.5[8] L☉
Surface gravity (log g)	1.0[5] cgs
Temperature	4,019±38[8] K
Metallicity [Fe/H]	0.17[7] dex
Rotational velocity (v sin i)	5.9[5] km/s
Age	3.53[7] Gyr
Other designations
υ Gem, 69 Geminorum, BD+27°1424, FK5 1196, HD 60522, HIP 36962, HR 2905, SAO 79533.[9]
Database references
SIMBAD	data

This is an evolved red giant star with a stellar classification of M0 III.^[4] It is estimated to have 1.52^[7] times the mass of the Sun, but has expanded to 40^[8] times the Sun's radius. The star is spinning with a projected rotational velocity of 5.9 km/s^[5] and is about 3.53^[7] billion years old. Upsilon Geminorum is radiating 370 times the solar luminosity from its outer atmosphere at an effective temperature of 4,019 K.^[8]

Based upon the motion of this star through space, Upsilon Geminorum is a member of the Wolf 630 moving group. This is a set of stars centered on Wolf 630 that are moving nearly in parallel and have an age of around 2.7±0.5 billion years. They may be former members of a dissolved open cluster.^[11]