Beta Piscium

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Beta Piscium
Diagram showing star positions and boundaries of the Pisces constellation and its surroundings
Cercle rouge 100%.svg
Location of β Piscium (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pisces
Right ascension 23h 03m 52.61349s[1]
Declination +03° 49′ 12.1662″[1]
Apparent magnitude (V) +4.40[2]
Spectral type B6Ve[3]
U−B color index −0.48[4]
B−V color index −0.12[4]
Variable type Suspected[5]
Radial velocity (Rv) 0.0 ± 0.6[6] km/s
Proper motion (μ) RA: 11.76[1] mas/yr
Dec.: −9.85[1] mas/yr
Parallax (π) 7.99 ± 0.22[1] mas
Distance 410 ± 10 ly
(125 ± 3 pc)
Absolute magnitude (MV) −1.01[7]
Mass 4.7 M
Radius 3.6 R
Luminosity 523.6[8] L
Surface gravity (log g) 4.0 cgs
Temperature 15500 K
Rotational velocity (v sin i) 90 ± 15 km/s
Other designations
β Psc, 4 Psc, BD+03° 4818, FK5 1602, HD 217891, HIP 113889, HR 8773, SAO 127934[9]
Database references

Beta Piscium (β Piscium), also known by its traditional name Fum al Samakah, is a blue-white hued star in the zodiac constellation of Pisces. Its apparent magnitude is 4.40,[2] meaning it can be faintly seen with the naked eye. Based on parallax estimates made by the Hipparcos spacecraft, the system is located about 410 light-years (125 parsecs) away.[1]

Beta Piscium is a Be star,[9] a special class of B-type stars with emission lines in their spectra. With a spectral type of B6Ve[3] its mass is estimated to be about 4.7 M, and its radius is about 3.6 M.[3] It is suspected to be a variable star.[5] Beta Piscium is radiating 524[8] times the Sun's luminosity from its photosphere at an effective temperature of 15,500 K.[3] The star has a high rate of spin, showing a projected rotational velocity of around 90 km/s.[8]

Name and etymology[edit]

  • The name Fum al Samakah was from the Arabic فم السمكة fum al-samakah "mouth of the fish" (compare Fomalhaut).[10][11]
  • In Chinese, 霹靂 (Pī Lì), meaning Thunderbolt, refers to an asterism consisting of refers to an asterism consisting of β Piscium, γ Piscium, θ Piscium, ι Piscium and ω Piscium. Consequently, β Piscium itself is known as 霹靂一 (Pī Lì yī, English: the First Star of Thunderbolt.)[12]


  1. ^ a b c d e f van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  2. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D. 
  3. ^ a b c d e Jones, C. E.; Tycner, C.; Sigut, T. A. A.; Benson, J. A.; Hutter, D. J. (2008). "A Parameter Study of Classical Be Star Disk Models Constrained by Optical Interferometry". The Astrophysical Journal. 687: 598–607. arXiv:0807.1515Freely accessible. Bibcode:2008ApJ...687..598J. doi:10.1086/591726. 
  4. ^ a b Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971). "Four-color, Hbeta, and UBV photometry for bright B-type stars in the northern hemisphere". The Astronomical Journal. 76: 1058. Bibcode:1971AJ.....76.1058C. doi:10.1086/111220. 
  5. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S. 
  6. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053Freely accessible. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. 
  7. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  8. ^ a b c Zorec, J.; Royer, F. (January 2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052Freely accessible, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691. 
  9. ^ a b "* bet Psc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 April 2017. 
  10. ^ HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index, Kostjuk 2002, refer to table3.dat
  11. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Pisces, the Fishes
  12. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 8 日