Alpha Piscium

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Alpha Piscium
Diagram showing star positions and boundaries of the Pisces constellation and its surroundings
Cercle rouge 100%.svg

Location of α Piscium(circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pisces
Right ascension 02h 02m 02.81972s[1]
Declination +02° 45′ 49.5410″[1]
Apparent magnitude (V) 3.82[2] (+4.33 + 5.23)[3]
Distance 139 ± 1.6 ly
(46.2 ± 0.5[1] pc)
Spectral type A0pSiSr + A3m[3]
Other designations
Alrischa, Alrescha, Kaitain, Okda, α Piscium, α Psc, Alpha Psc, 113 Piscium, BD+02 317, CCDM J02020+0246AB, HD 12447/12446, HIP 9487, HR 595/596, IDS 01569+0217 AB / 02020+0246, SAO 110291, WDS J02020+0246AB.[2]

Alpha Piscium (Alpha Psc, α Piscium, α Psc) is the Bayer designation for a star in the equatorial constellation of Pisces. It has the traditional name Alrescha (Al Rescha, Alrischa, Alrisha).

The distance to α Psc is about 139 light years. The system comprises a close double star with angular separation of presently 1.8" between the components. The main star is of magnitude +4.33 and spectral type A0p, while the companion is magnitude 5.23 and belongs to spectral class A3m. The two stars take more than 700 years to orbit one another and they will make their closest approach to each other around 2060. One or both of the stars may be a spectroscopic binary as well. The stars have masses of 2.3 and 1.8 solar masses respectively and shine with a total luminosity of 31 and 12 times that of the Sun.[4]

Name and etymology[edit]

  • The name Alrescha is from the Arabic الرشآء al-rišā’ "the well rope". Less common names are Kaitain and Okda, the latter from the Arabic عقدة ‘uqdah "knot".[5]
  • In Chinese, 外屏 (Wài Píng), meaning Outer Fence, refers to an asterism consisting of α Piscium, δ Piscium, ε Piscium, ζ Piscium, μ Piscium, ν Piscium and ξ Piscium. Consequently, α Piscium itself is known as 外屏七 (Wài Píng qī, English: the Seventh Star of Outer Fence.)[6]


  1. ^ a b c van Leeuwen, F. (November 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. 
  2. ^ a b "alf Psc -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg). 
  3. ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819. 
  4. ^ Kaler, James B., "ALRESCHA (Alpha Piscium)", Stars (University of Illinois), retrieved 2012-04-06. 
  5. ^ Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 506. 
  6. ^ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 19 日