6 Andromedae

6 Andromedae is an astrometric binary star^[7] system in the northern constellation of Andromeda. The designation comes from the star catalogue of John Flamsteed, first published in 1712. Its apparent visual magnitude is 5.91,^[2] which is just bright enough to be visible to the naked eye under good seeing conditions. Based upon an annual parallax shift of 34.1 mas as seen from Earth,^[1] it is around 96 light years from the Sun. It is moving closer to the Sun with a radial velocity of −32.4 km/s.^[2] The system has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.272 arc seconds per annum.^[8]

This is a single-lined spectroscopic binary with an orbital period of 9.2 years and an eccentricity of 0.3.^[3] Some early observations of the star gave it a subgiant luminosity class and it was published in the Bright Star Catalogue as spectral class F5 IV. More modern measurements identify the visible component as an F-type main-sequence star with a stellar classification of F5 V.^[3][9] The star is an estimated 2.9^[4] billion years old with 1.3^[4] times the mass of the Sun and 1.5^[1] times the Sun's radius. It is radiating 3.1^[1] times the Sun's luminosity from its photosphere at an effective temperature of around 6,425 K.^[4] 6 Andromedae displays an infrared excess at a wavelength of 22 μm, which may indicate a circumstellar disk of warm dusty debris.^[5]

The mass of the secondary component is roughly at or above that of the Sun. If it were a single, ordinary star, it should be readily visible as it would be just one magnitude fainter than the primary. The lack of conspicuous ultraviolet emission appears to rule out a white dwarf companion, so it may instead itself be a binary system consisting of two smaller stars having an orbital period between a week and a year.^[3]