Astronomy:Beta Pegasi

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Short description: Red giant star in the constellation Pegasus
Beta Pegasi
Pegasus constellation map.svg
Red circle.svg
Location of β Pegasi (circled)
Observation data
Equinox J2000.0]] (ICRS)
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]
Characteristics
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]
Astrometry
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
Distance196 ± 2 ly
(60.1 ± 0.5 pc)
Absolute magnitude (MV)−1.41[7]
Details
Mass2.1[8] M☉
Radius95 R☉
Surface gravity (log g)1.20[9] cgs
Temperature3,689[9] K
Metallicity [Fe/H]−0.11[9] dex
Rotational velocity (v sin i)9.7[10] km/s
Other designations
Scheat, 53 Pegasi, HR 8775, BD+27°4480, HD 217906, SAO 90981, FK5 870, HIP 113881[4]
Database references
SIMBADdata

Beta Pegasi (β Pegasi, abbreviated Beta Peg, β Peg), formally named Scheat /ˈʃiːæt/,[11][12] 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,[13] a prominent rectangular asterism.

Nomenclature

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.[13] In 2016, the International Astronomical Union organised a Working Group on Star Names (WGSN)[14] to catalog and standardise proper names for stars. The WGSN's first bulletin of July 2016[15] 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[12]).

In Chinese, 室宿 (Shì Xiù), meaning Encampment, refers to an asterism consisting β Pegasi and α Pegasi.[16] Consequently, the Chinese name for β Pegasi itself is 室宿二 (Shì Xiù èr), "the Second Star of Encampment".[17]

Distance and properties

A light curve for Beta Pegasi, plotted from Hipparcos data[18]

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. 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 1,500 times that of the Sun. 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.[19] The photosphere is sufficiently cool for molecules of titanium oxide to form.[20]

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).[21]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V 
  2. ↑ 2.0 2.1 2.2 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. ↑ 3.0 3.1 "Query= bet Peg", General Catalogue of Variable Stars (Centre de Données astronomiques de Strasbourg), http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=bet+Peg, retrieved 2010-01-05 
  4. ↑ 4.0 4.1 4.2 "V* bet Peg -- Pulsating variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+217906, retrieved 2010-01-05 
  5. ↑ 5.0 5.1 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, doi:10.1111/j.1365-2966.2009.15588.x, Bibcode: 2009MNRAS.400.1945T 
  6. ↑ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington (Washington: Carnegie Institution of Washington), Bibcode: 1953GCRV..C......0W 
  7. ↑ Huang, W. et al. (2012), "A catalogue of Paschen-line profiles in standard stars", Astronomy & Astrophysics 547: A62, doi:10.1051/0004-6361/201219804, Bibcode: 2012A&A...547A..62H. 
  8. ↑ Tsuji, Takashi (May 2007), Kupka, F.; Roxburgh, I.; Chan, K., eds., "Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars", Convection in Astrophysics, Proceedings of the International Astronomical Union 2 (S239): 307–310, doi:10.1017/S1743921307000622, Bibcode: 2007IAUS..239..307T 
  9. ↑ 9.0 9.1 9.2 9.3 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, doi:10.1051/0004-6361:20078788, Bibcode: 2008A&A...480...91S 
  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, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M 
  11. ↑ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7. 
  12. ↑ 12.0 12.1 "IAU Catalog of Star Names". http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt. 
  13. ↑ 13.0 13.1 Allen, Richard Hinckley (1899), Star Names: Their Lore and Meaning, New York City , NY: Dover Publications Inc., p. 325, ISBN 0-486-21079-0, https://books.google.com/books?id=5xQuAAAAIAAJ&pg=PA325 
  14. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  15. ↑ "Bulletin of the IAU Working Group on Star Names, No. 1". http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf. 
  16. ↑ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN:978-986-7332-25-7.
  17. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  18. ↑ Light Curve, ESA, https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve, retrieved 21 September 2022. 
  19. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, retrieved 2012-01-16 
  20. ↑ 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 
  21. ↑ 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″



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