Upsilon Librae

Upsilon Librae (υ Lib, υ Librae) is the Bayer designation for a double star^[9] in the zodiac constellation Libra. With an apparent visual magnitude of 3.628,^[2] it is visible to the naked eye. The distance to this star, based upon an annual parallax shift of 14.58,^[1] is around 224 light years. It has a magnitude 10.8 companion at an angular separation of 2.0 arc seconds along a position angle of 151°, as of 2002.^[10]

Upsilon Librae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Libra
Right ascension	15h 37m 01.45020s[1]
Declination	−28° 08′ 06.2926″[1]
Apparent magnitude (V)	3.628[2]
Characteristics
Spectral type	K3 III[3]
U−B color index	+1.586[2]
B−V color index	+1.374[2]
Astrometry
Radial velocity (Rv)	−24.9±0.7[4] km/s
Proper motion (μ)	RA: −12.82[1] mas/yr Dec.: −4.15[1] mas/yr
Parallax (π)	14.58±0.19 mas[1]
Distance	224 ± 3 ly (68.6 ± 0.9 pc)
Absolute magnitude (MV)	−0.28[5]
Details[6]
Mass	1.67 M☉
Radius	31.5[7] R☉
Luminosity	309 L☉
Surface gravity (log g)	1.58 cgs
Temperature	4,135±20 K
Metallicity [Fe/H]	−0.02 dex
Age	3.14 Gyr
Other designations
υ Lib, 39 Lib, CD−27° 10464, FK5 579, HD 139063, HIP 76470, HR 5794, SAO 183619.[8]
Database references
SIMBAD	data

The brighter component is an evolved K-type giant star with a stellar classification of K3 III.^[3] The measured angular diameter, after correction for limb darkening, is 4.27±0.05 mas.^[11] At the estimated distance of the star, this yields a physical size of about 31.5 times the radius of the Sun.^[7] It has 1.67 times the mass of the Sun and radiates 309 times the solar luminosity from its outer atmosphere at an effective temperature of 4,135 K.^[6] The star is about three billion years old.^[6]

Upsilon Librae will be the brightest star in the night sky in about 2.3 million years,^[12] and will peak in brightness with an apparent magnitude of −0.46, or more than 40 times its present-day brightness.^[12]