Tau Piscium

Tau Piscium

Location of τ Piscium (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Pisces
Right ascension	01^h 11^m 39.63647^s[1]
Declination	+30° 05′ 22.6909″[1]
Apparent magnitude (V)	+4.518[2]
Characteristics
Spectral type	K0.5 IIIb[3]
U−B color index	+1.016[2]
B−V color index	+1.094[2]
Astrometry
Radial velocity (Rv)	36.36±0.34[4] 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[5]
Details[4]
Mass	1.69[6] 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[4] Gyr
Other designations
τ Psc, 83 Piscium, BD+29° 190, FK5 43, HD 7106, HIP 5586, HR 352, SAO 74546[7]
Database references
SIMBAD	data

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.[5]

This is an evolved K-type giant star with a stellar classification of K0.5 IIIb.[3] It is about 2.27[4] billion years and is a red clump star on the horizontal branch, which indicates it is generating energy through helium fusion at its core.[8] The star has 1.7[6] times the mass of the Sun and has expanded to about 10 times the Sun's radius.[4] It is radiating 45 times the Sun's luminosity from its photosphere at an effective temperature of 4,624 K.[4]

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]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Jennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants", Monthly Notices of the Royal Astronomical Society, 172 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
4. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
5. Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121.
6. Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
7. "tau Psc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-24.
8. Mishenina, T. V.; et al. (September 2006), "Elemental abundances in the atmosphere of clump giants", Astronomy and Astrophysics, 456 (3): 1109–1120, arXiv:astro-ph/0605615, Bibcode:2006A&A...456.1109M, doi:10.1051/0004-6361:20065141, S2CID 18764566.
9. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日 Archived 2016-03-03 at the Wayback Machine