Astronomy:Beta Pegasi
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 |
Distance | 196 ± 2 ly (60.1 ± 0.5 pc) |
Absolute magnitude (MV) | −1.41[7] |
Details | |
Mass | 2.1[8] M☉ |
Radius | 95 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 | |
Database references | |
SIMBAD | data |
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
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
- ↑ 1.0 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
- ↑ 2.0 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.
- ↑ 3.0 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
- ↑ 4.0 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
- ↑ 5.0 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
- ↑ Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Washington (Washington: Carnegie Institution of Washington), Bibcode: 1953GCRV..C......0W
- ↑ 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.
- ↑ 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
- ↑ 9.0 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
- ↑ 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
- ↑ 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.
- ↑ 12.0 12.1 "IAU Catalog of Star Names". http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt.
- ↑ 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
- ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/.
- ↑ "Bulletin of the IAU Working Group on Star Names, No. 1". http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf.
- ↑ (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.
- ↑ (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.
- ↑ Light Curve, ESA, https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve, retrieved 21 September 2022.
- ↑ "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
- ↑ 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
- ↑ 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: 23h 03m 46.458s, +28° 04′ 58.04″
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