Tau Piscium

Tau Piscium (τ Piscium) is an orange-hued star in the zodiac constellation of Pisces. With an apparent visual magnitude of +4.52,^[2] it is a dim star but visible to the naked eye. Based upon an annual parallax shift of 19.32 mas as seen from Earth,^[1] it is located around 169 light years from the Sun. It is most likely (96% chance) a member of the thin disk population.^[6]

Tau Piscium

Location of τ Piscium (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Pisces
Right ascension	01h 11m 39.63647s[1]
Declination	+30° 05′ 22.6909″[1]
Apparent magnitude (V)	+4.518[2]
Characteristics
Evolutionary stage	red clump[3]
Spectral type	K0.5 IIIb[4]
U−B color index	+1.016[2]
B−V color index	+1.094[2]
Astrometry
Radial velocity (Rv)	36.36±0.34[5] km/s
Proper motion (μ)	RA: +73.88[1] mas/yr Dec.: −38.30[1] mas/yr
Parallax (π)	19.32±0.24 mas[1]
Distance	169 ± 2 ly (51.8 ± 0.6 pc)
Absolute magnitude (MV)	+1.033[6]
Details[5]
Mass	1.69[7] M☉
Radius	10 R☉
Luminosity	44.7 L☉
Surface gravity (log g)	2.6 cgs
Temperature	4,624±5 K
Metallicity [Fe/H]	−0.04 dex
Rotational velocity (v sin i)	2.2 km/s
Age	2.27[5] Gyr
Other designations
τ Psc, 83 Piscium, BD+29°190, FK5 43, HD 7106, HIP 5586, HR 352, SAO 74546[8]
Database references
SIMBAD	data

This is an evolved K-type giant star with a stellar classification of K0.5 IIIb.^[4] It is about 2.27^[5] billion years and is a red clump star on the horizontal branch, which indicates it is generating energy through helium fusion at its core.^[3] The star has 1.7^[7] times the mass of the Sun and has expanded to about 10 times the Sun's radius.^[5] It is radiating 45 times the Sun's luminosity from its photosphere at an effective temperature of 4,624 K.^[5]

Naming

In Chinese, 奎宿 (Kuí Sù), meaning Legs, refers to an asterism consisting of τ Piscium, η Andromedae, 65 Piscium, ζ Andromedae, ε Andromedae, δ Andromedae, π Andromedae, ν Andromedae, μ Andromedae, β Andromedae, σ Piscium, 91 Piscium, υ Piscium, φ Piscium, χ Piscium and ψ¹ Piscium. Consequently, the Chinese name for τ Piscium itself is 奎宿十一 (Kuí Sù shíyī, English: the Eleventh Star of Legs.)^[9]