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  • 21 Aug, 2019

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Beta Pegasi
Beta Pegasi (β Pegasi, abbreviated Beta Peg, β Peg), formally named Scheat /ˈʃiːæt/, 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, 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. In 2016, the International Astronomical Union organised a Working Group on Star Names (WGSN) to catalog and standardise proper names for stars. The WGSN's first bulletin of July 2016 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).

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

Distance and properties

A light curve for Beta Pegasi, plotted from Hipparcos data

Based upon parallax measurements, Beta Pegasi is located about 196 light-years (60 parsecs) from the Sun. 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, which indicates the spectrum has characteristics partway between a bright giant and a giant star. It has expanded until it is 109 times as large, and has a total luminosity of 1,640 times that of the Sun. The effective temperature of the star's outer envelope is about 3,600 K, giving the star the characteristic orange-red hue of an M-type star. The photosphere is sufficiently cool for molecules of titanium oxide to form.

Beta Pegasi is a semi-regular variable with a period of 43.3 days and a brightness that varies from magnitude +2.31 to +2.74 (averaging 2.42). It is losing mass at a rate at or below 10 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).

Notes

  1. ^ Calculated from bolometric magnitude in the equation 10, where "Mbol" is the bolometric magnitude.

References

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  9. ^ Arroyo-Torres, B.; et al. (June 2014). "VLTI/AMBER observations of cold giant stars: atmospheric structures and fundamental parameters". Astronomy & Astrophysics. 566: 11. arXiv:1404.7384. Bibcode:2014A&A...566A..88A. doi:10.1051/0004-6361/201323264. S2CID 16778588. A88.{{cite journal}}: CS1 maint: postscript (link)
  10. ^ 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, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121
  11. ^ 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, S2CID 121883397
  12. ^ 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.
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  14. ^ Allen, Richard Hinckley (1899), Star Names: Their Lore and Meaning, New York, NY: Dover Publications Inc., p. 325, ISBN 0-486-21079-0
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  17. ^ (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.
  18. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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  21. ^ 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
  22. ^ 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.


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