Tau Piscium
Orange-hued star in the constellation Pisces
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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]
 | |
| 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]