Beta Pegasi

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Red giant star in the constellation Pegasus

title: "Beta Pegasi" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["bayer-objects", "m-type-bright-giants", "m-type-giants", "pegasus-(constellation)", "stars-with-proper-names", "flamsteed-objects", "bright-star-catalogue-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "durchmusterung-objects", "semiregular-variable-stars", "emission-line-stars", "asymptotic-giant-branch-stars"] description: "Red giant star in the constellation Pegasus" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Beta_Pegasi" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Red giant star in the constellation Pegasus ::

| name=Beta Pegasi | image= |image=Pegasus constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=12|mark_link=Beta Pegasi|x=409|y=294 |caption=Location of β Pegasi (circled) | epoch = J2000 | ra = | dec = | appmag_v = 2.42 (2.312.74) | constell = Pegasus | type = AGB | class = M2.5II–IIIe | b-v = +1.67 | u-b = +1.96 | variable = Semi-regular | radial_v = +8.7 | prop_mo_ra = +187.65 | prop_mo_dec = +136.93 | parallax = 16.64 | p_error = 0.15 | parallax_footnote = | dist_footnote =
| absmag_v = −1.41 | mass = | radius = | luminosity = 1,644 | temperature = 3,606 | gravity = 1.20 | metal_fe = −0.11 | rotational_velocity = 9.7 | age = | names = Scheat, 53 Pegasi, HR 8775, BD+27°4480, HD 217906, SAO 90981, FK5 870, HIP 113881 | Simbad=HD+217906

Beta Pegasi (β Pegasi, abbreviated Beta Peg, β Peg), formally named Scheat , 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

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/74/BetaPegLightCurve.png" caption="A [[light curve]] for Beta Pegasi, plotted from ''[[Hipparcos]]'' data"] ::

Based upon parallax measurements, Beta Pegasi is located about 196 ly 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.

Johann Friedrich Julius Schmidt discovered that Beta Pegasi is a variable star, in 1847. 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 10−8 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).

Notes

References

References

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  2. {{in lang. zh [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ala_alz.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive. link. (2008-10-25 , Hong Kong Space Museum. Accessed on line November 23, 2010.)
  3. {{in lang. zh ''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.
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  11. Wilson, Ralph Elmer. (1953). "General Catalogue of Stellar Radial Velocities". [[Carnegie Institution of Washington]].
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  13. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory.
  14. (2015-08-01). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society.
  15. "V* bet Peg -- Pulsating variable Star". [[Centre de Données astronomiques de Strasbourg]].
  16. (December 2009). "Long-term photometry and periods for 261 nearby pulsating M giants". [[Monthly Notices of the Royal Astronomical Society]].
  17. "Query= bet Peg". [[Centre de Données astronomiques de Strasbourg]].
  18. (1899). "Star Names: Their Lore and Meaning". [[Dover Publications]] Inc..
  19. (November 1992). "K I/Na I scattering observations in circumstellar envelopes - Alpha(1) Herculis, Omicron Ceti, TX PISCIUM and Beta Pegasi". Astronomy and Astrophysics.
  20. (February 1996). "Stellar spectroscopy with CCDs - some preliminary results". Journal of the British Astronomical Association.
  21. (December 21, 2004). "The Colour of Stars". [[Commonwealth Scientific and Industrial Research Organisation]].

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bayer-objectsm-type-bright-giantsm-type-giantspegasus-(constellation)stars-with-proper-namesflamsteed-objectsbright-star-catalogue-objectshenry-draper-catalogue-objectshipparcos-objectsdurchmusterung-objectssemiregular-variable-starsemission-line-starsasymptotic-giant-branch-stars