Tau3 Serpentis

Tau³ Serpentis, Latinized from τ³ Serpentis, is a giant star in the constellation of Serpens. It has an apparent visual magnitude of approximately 6.11,^[2] which is bright enough to be dimly visible to the naked eye under favorable viewing conditions. The distance to this star is approximately 358 light years based on parallax measurements, but it is drifting closer with a heliocentric radial velocity of −22 km/s.^[6]

For other stars with this Bayer designation, see Tau Serpentis.

τ³ Serpentis

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Serpens
Right ascension	15h 35m 33.230s[1]
Declination	+17° 39′ 20.00″[1]
Apparent magnitude (V)	6.10[2]
Characteristics
Spectral type	G8III:[3]
B−V color index	+0.975±0.006[2]
Astrometry
Radial velocity (Rv)	−22.3±2.9[4] km/s
Proper motion (μ)	RA: −77.745 mas/yr[1] Dec.: −13.437 mas/yr[1]
Parallax (π)	9.1014±0.0329 mas[1]
Distance	358 ± 1 ly (109.9 ± 0.4 pc)
Absolute magnitude (MV)	+0.78[2]
Details[1]
Mass	2.703+0.107 −0.040 M☉
Radius	9.68+0.20 −0.19 R☉
Luminosity	47.28+0.33 −0.31 L☉
Surface gravity (log g)	2.478±0.005 cgs
Temperature	4,864±1 K
Age	502+51 −69 Myr
Other designations
τ3 Ser, 15 Serpentis, BD+18°3044, FK5 3230, GC 20962, HD 139074, HIP 76337, HR 5795, SAO 101631, PPM 131527[5]
Database references
SIMBAD	data

The stellar classification of this star is G8III:,^[3] which matches a G-type giant star. However, the trailing colon ':' indicates some uncertainty in the classification. About 500 million years old and with 2.7 times the mass of the Sun, Tau³ Serpentis has expanded to 9.7 times the Sun's radius, and is radiating 47 times the luminosity of the Sun from its photosphere at an effective temperature of 4,864 K.^[1]