Magnitude 3 Apparent magnitude (V) 3 | Constellation Triangulum | |
 | ||
Similar Alpha Trianguli, Iota Trianguli, Delta Trianguli, Alpha Trianguli Australis, Beta Herculis | ||
Beta Trianguli (Beta Tri, β Trianguli, β Tri) is the Bayer designation for a binary star system in the constellation Triangulum, located about 127 light years from Earth. Although the apparent magnitude is only 3.0, it is the brightest star in the constellation Triangulum.
The star Beta Trianguli has a stellar classification of A5IV, indicating that it has evolved away from the main sequence and is now a giant star, but the classification is uncertain and not consistent with the mass derived from the orbit. It is among the least variable of the stars that were observed by the Hipparcos spacecraft, with a magnitude varying by only 0.0005. This is a probable spectroscopic binary star system with an orbital period of 31.39 days and an eccentricity of 0.43. They are separated by a distance of less than 5 AU.
Based on observations using the Spitzer Space Telescope, as reported in 2005, this system is emitting an excess of infrared radiation. This emission can be explained by a circumbinary ring of dust. The dust is emitting infrared radiation at a blackbody temperature of 100 K. It is thought to extend from 50 to 400 AU away from the stars.