Theta Piscium
Location of θ Piscium (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pisces
Right ascension 23h 27m 58.09529s[1]
Declination +6° 22′ 44.3720″[1]
Apparent magnitude (V) 4.27[2]
Characteristics
Spectral type K1 III[2]
U−B color index +1.00
B−V color index +1.062[2]
Astrometry
Radial velocity (Rv)+6.05±0.19[2] km/s
Proper motion (μ) RA: −123.83[1] mas/yr
Dec.: −43.26[1] mas/yr
Parallax (π)21.96 ± 0.25 mas[1]
Distance149 ± 2 ly
(45.5 ± 0.5 pc)
Absolute magnitude (MV)+0.83[2]
Details
Mass1.58[3] M☉
Radius11[4] R☉
Luminosity51.3[4] L☉
Surface gravity (log g)2.70[5] cgs
Temperature4,684±23[3] K
Metallicity [Fe/H]0.06[5] dex
Rotational velocity (v sin i)3.1[4] km/s
Age2.45[3] Myr
Other designations
θ Psc, 10 Piscium, BD+05° 5173, FK5 1614, GC 32647, HD 220954, HIP 115830, HR 8916, SAO 128196, PPM 174110[6]
Database references
SIMBADdata

Theta Piscium, Latinized from θ Piscium, is a single,[7] orange-hued star in the zodiac constellation of Pisces, the fish. The annual parallax shift of this star was measured during the Hipparcos mission as 21.96 mas,[1] which yields a distance estimate of about 149 light years. It is a faint star but visible to the naked eye with an apparent visual magnitude of 4.27.[2] The star is moving away from the Sun with a radial velocity of +6 km/s.[2]

At the estimated age of 2.5 billion years,[3] this is an aging giant star with a stellar classification of K1 III,[2] which means it has exhausted the supply of hydrogen at its core. It is a red clump star, indicating it is on the horizontal branch of its evolution and is generating energy through helium fusion at its core.[5] Theta Piscium has 158%[3] of the Sun's mass and its outer atmosphere has swollen to about 11[4] times the girth of the Sun. It is brighter yet cooler than the Sun, radiating 51.3[4] times the Sun's luminosity from its enlarged photosphere at an effective temperature of about 4,684 K.[3]

Naming

In Chinese, 霹靂 (Pī Lì), meaning Thunderbolt, refers to an asterism consisting of refers to an asterism consisting of θ Piscium, β Piscium, γ Piscium, ι Piscium and ω Piscium. Consequently, the Chinese name for θ Piscium itself is 霹靂三 (Pī Lì sān, English: the Third Star of Thunderbolt.)[8]

References

  1. 1 2 3 4 5 6 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. 1 2 3 4 5 6 7 8 Hekker, S.; et al. (August 2006), "Precise radial velocities of giant stars. I. Stable stars", Astronomy and Astrophysics, 454 (3): 943–949, arXiv:astro-ph/0604502, Bibcode:2006A&A...454..943H, doi:10.1051/0004-6361:20064946, S2CID 119529768.
  3. 1 2 3 4 5 6 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", Astronomical Journal, 150 (3), 88, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114.
  4. 1 2 3 4 5 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. 1 2 3 Liu, Y. J.; et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society, 382 (2): 553–66, Bibcode:2007MNRAS.382..553L, doi:10.1111/j.1365-2966.2007.11852.x.
  6. ↑ "tet Lib". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-12-17.
  7. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
  8. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 8 日
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