Theta_Pegasi
Theta Pegasi
Single star in the constellation Pegasus
θ Pegasi, Latinized as Theta Pegasi, is a single[8] star in the equatorial constellation of Pegasus, lying about 7.5 degrees southwest of Enif.[9] It has the traditional name Biham /ˈbaɪ.æm/,[10][11] 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.[2] 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.[2]
This object an A-type main-sequence star with a stellar classification of A2V.[4] It is 448[6] million years old with a high rate of spin, showing a projected rotational velocity of 136 km/s.[6] This star has 2.09[5] times the mass of the Sun and 2.6[12] 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.[12] The star appears to display a slight infrared excess.[13]
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.[5] It is a red dwarf with a spectral type of M4 to M5.5, and a luminosity of 0.5% that of the Sun.[5] The orbit around the primary is estimated to be moderately eccentric, at 0.54, and has a semimajor axis of 6.55 au.[5]