Theta Pegasi
Single star in the constellation Pegasus
title: "Theta Pegasi" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["a-type-main-sequence-stars", "m-type-main-sequence-stars", "binary-stars", "pegasus-(constellation)", "bayer-objects", "durchmusterung-objects", "flamsteed-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "bright-star-catalogue-objects", "stars-with-proper-names"] description: "Single star in the constellation Pegasus" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Theta_Pegasi" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0
::summary Single star in the constellation Pegasus ::
| image = | image=Pegasus IAU.svg | float=center | width=250 | position=right | mark=Red circle.svg | mark_width=10 | mark_link=θ Peg | x%=56.0 | y%=63.5 | caption = Location of θ Pegasi (circled) | epoch = J2000.0 | constell = Pegasus | ra = | dec = | appmag_v = +3.52 | type = main sequence | class = A2V + M4-5.5 | b-v = | u-b = | variable = | radial_v = | prop_mo_ra = +282.18 | prop_mo_dec = +30.46 | parallax = 35.34 | p_error = 0.85 | parallax_footnote = | absmag_v = 1.24 | reference = | axis_unitless = au | eccentricity = | inclination = | component1 = θ Peg A | mass = 2.09 ± 0.16 | radius = | gravity = 3.95 | age_myr = 448 | metal_fe = −0.38 | luminosity = | temperature = | rotational_velocity = 136 | component2 = θ Peg B | mass2 = | temperature2 = 3200 | gravity2 = 5.5 | names = |Simbad=*+tet+Peg
θ Pegasi, Latinized as Theta Pegasi, is a binary star in the equatorial constellation of Pegasus, lying about 7.5 degrees southwest of Enif. It has the traditional name Biham , and the Flamsteed designation 26 Pegasi. This object is visible to the naked eye as a white-hued point of light with an apparent visual magnitude of +3.52. The system is located 92 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −8 km/s.
This object is an A-type main-sequence star with a stellar classification of A2V. It is 448 million years old with a high rate of spin, with a projected rotational velocity of 136 km/s. This star has 2.09 times the mass of the Sun and 2.6 times the Sun's radius. It is radiating 25 times the luminosity of the Sun from its outer envelope at an effective temperature of 7,951 K. The star appears to display a slight infrared excess.
θ Pegasi was suspected of being a binary star due to an acceleration detected by Hipparcos. In 2021, a low-mass companion star was discovered, associated with θ Pegasi.
Nomenclature
θ Pegasi (Latinised to Theta Pegasi) is the star's Bayer designation.
It bore the traditional name Biham or Baham from the Arabic phrase s'ad al Biham "Lucky Stars of the Young Beasts". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Biham for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, 危宿 (Wēi Sù), meaning Rooftop, refers to an asterism consisting of Theta Pegasi, Alpha Aquarii and Epsilon Pegasi. Consequently, the Chinese name for Theta Pegasi itself is 危宿二 (Wēi Sù èr, .)
References
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| last1=Boyajian | first1=Tabetha S. | last2=McAlister | first2=Harold A. | last3=van Belle | first3=Gerard | last4=Gies | first4=Douglas R. | last5=ten Brummelaar | first5=Theo A. | last6=von Braun | first6=Kaspar | last7=Farrington | first7=Chris | last8=Goldfinger | first8=P. J. | last9=O'Brien | first9=David | last10=Parks | first10=J. Robert | last11=Richardson | first11=Noel D. | last12=Ridgway | first12=Stephen | last13=Schaefer | first13=Gail | last14=Sturmann | first14=Laszlo | last15=Sturmann | first15=Judit | last16=Touhami | first16=Yamina | last17=Turner | first17=Nils H. | last18=White | first18=Russel | title=Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars | display-authors=1 | journal=The Astrophysical Journal | volume=746 | issue=1 | page=101 | date=February 2012 | doi=10.1088/0004-637X/746/1/101 | postscript=. | bibcode=2012ApJ...746..101B | arxiv=1112.3316 | s2cid=18993744 }}. See Table 10.
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| first=James B. | last=Kaler | work=STARS | title=Biham | date=October 15, 2010 | url=http://stars.astro.illinois.edu/sow/biham.html }}
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References
- (2021). "SCExAO/MEC and CHARIS Discovery of a Low-mass, 6 au Separation Companion to HIP 109427 Using Stochastic Speckle Discrimination and High-contrast Spectroscopy". The Astronomical Journal.
- {{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.
- {{in lang. zh [http://www.lcsd.gov.hk/CE/Museum/Space/Research/StarName/c_research_chinengstars_ama_b.htm 香港太空館 - 研究資源 - 亮星中英對照表] {{webarchive. link. (2010-08-11 , Hong Kong Space Museum. Accessed on line November 23, 2010.)
- "tet Peg".
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