Beta Pegasi

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Beta Pegasi
Pegasus constellation map.svg
Red circle.svg

Location of β Pegasi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Pegasus
Right ascension 23h 03m 46.45746s[1]
Declination +28° 04′ 58.0336″[1]
Apparent magnitude (V) 2.42[2] (2.31 - 2.74)[3]
Spectral type M2.5II–IIIe[4]
U−B color index +1.96[2]
B−V color index +1.67[2]
Variable type Semi-regular[5]
Radial velocity (Rv) +8.7[6] km/s
Proper motion (μ) RA: +187.65[1] mas/yr
Dec.: +136.93[1] mas/yr
Parallax (π) 16.64 ± 0.15[1] mas
Distance 196 ± 2 ly
(60.1 ± 0.5 pc)
Absolute magnitude (MV) -1.49
Mass 2.1[7] M
Radius 95[8] R
Surface gravity (log g) 1.20[9] cgs
Temperature 3,689[9] K
Metallicity [Fe/H] –0.11[9] dex
Rotational velocity (v sin i) 9.7[10] km/s
Other designations
Scheat, 53 Peg, HR 8775, BD +27°4480, HD 217906, SAO 90981, FK5 870, HIP 113881.[4]
Database references

Beta Pegasi (β Pegasi, abbreviated Beta Peg, β Peg), also named Scheat,[11] is a red giant star and the second brightest star (after Epsilon Pegasi) in the constellation of Pegasus. It forms the upper right corner of the Great Square of Pegasus,[12] a prominent rectangular asterism.


β Pegasi (Latinised to Beta Pegasi) is the star's Bayer designation.

It bore the traditional name of Scheat, a name that had also been used for Delta Aquarii. The name was derived from the Arabic Al Sā'id "the upper arm", or from Sa'd.[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Scheat for this star (the name Skat was later approved for Delta Aquarii[11]).

Arabian astronomers named it Mankib al Faras, meaning the "Horse's shoulder".

Distance and properties[edit]

Based upon parallax measurements, Beta Pegasi is located about 196 light-years (60 parsecs) from the Sun.[1] It is unusual among bright stars in having a relatively cool surface temperature compared to stars like the Sun.[8] This star has a stellar classification of M2.3 II–III,[4] which indicates the spectrum has characteristics partway between a bright giant and a giant star. It has expanded until it is some 95 times as large, and has a total luminosity of 1500 times that of the Sun.[8] The effective temperature of the star's outer envelope is about 3,700 K,[9] giving the star the characteristic orange-red hue of an M-type star.[15] The photosphere is sufficiently cool for molecules of titanium oxide to form.[16]

Beta Pegasi is a semi-regular variable with a period of 43.3 days[5] and a brightness that varies from magnitude +2.31 to +2.74 (averaging 2.42).[3] It is losing mass at a rate at or below 10−8 times the Sun's mass per year, which is creating an expanding shell of gas and dust with a radius of about 3,500 times the Sun's radius (16 Astronomical Units).[17]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357 
  2. ^ a b c Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J. 
  3. ^ a b "Query= bet Peg", General Catalogue of Variable Stars, Centre de Données astronomiques de Strasbourg, retrieved 2010-01-05 
  4. ^ a b c "V* bet Peg -- Pulsating variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2010-01-05 
  5. ^ a b Tabur, V.; et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–1961, Bibcode:2009MNRAS.400.1945T, arXiv:0908.3228Freely accessible, doi:10.1111/j.1365-2966.2009.15588.x 
  6. ^ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W 
  7. ^ Tsuji, Takashi (May 2007). "Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars". In Kupka, F.; Roxburgh, I.; Chan, K. Convection in Astrophysics, Proceedings of IAU Symposium #239 held 21-25 August, 2006 in Prague, Czech Republic. Proceedings of the International Astronomical Union. 2. pp. 307–310. Bibcode:2007IAUS..239..307T. arXiv:astro-ph/0610180Freely accessible. doi:10.1017/S1743921307000622. 
  8. ^ a b c Kaler, James B. (May 22, 2009), "SCHEAT (Beta Pegasi)", Stars, University of Illinois, retrieved 2010-01-05 
  9. ^ a b c d 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, Bibcode:2008A&A...480...91S, arXiv:0712.1370Freely accessible, doi:10.1051/0004-6361:20078788 
  10. ^ 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 
  11. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  12. ^ a b Allen, Richard Hinckley (1899), Star Names: Their Lore and Meaning, New York, NY: Dover Publications Inc., p. 325, ISBN 0-486-21079-0 
  13. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016. 
  14. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016. 
  15. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-10, retrieved 2012-01-16 
  16. ^ Gavin, M. (February 1996), "Stellar spectroscopy with CCDs - some preliminary results", Journal of the British Astronomical Association, 106 (1): 11–15, Bibcode:1996JBAA..106...11G 
  17. ^ Mauron, N.; Caux, E. (November 1992), "K I/Na I scattering observations in circumstellar envelopes - Alpha(1) Herculis, Omicron Ceti, TX PISCIUM and Beta Pegasi", Astronomy and Astrophysics, 265 (2): 711–725, Bibcode:1992A&A...265..711M . Solar Radius = 0.0046491 AU.

Coordinates: Sky map 23h 03m 46.458s, +28° 04′ 58.04″