Sigma Andromedae

Template:Starbox begin Template:Starbox image Template:Starbox observe Template:Starbox character Template:Starbox astrometry Template:Starbox detail Template:Starbox catalog Template:Starbox reference Template:Starbox end Sigma Andromedae (σ And, σ Andromedae) is the Bayer designation for a star in the northern constellation of Andromeda. It has an apparent visual magnitude of +4.5, which is bright enough to be seen with the naked eye from most locations. Parallax measurements made during the Hipparcos mission place it at a distance of about Template:Convert. The magnitude of the star is diminished by 0.08 from extinction caused by intervening gas and dust.

This star has a stellar classification of A2 V, which matches the spectrum of an A-type main sequence star. It is about 450 million years old and is spinning rapidly with a projected rotational velocity of 123 km/s. The interferometry-measured angular diameter of this star is 0.465 mas, which, at its estimated distance, equates to a physical radius of about 2.1 times the radius of the Sun. It is radiating 26 times the luminosity of the Sun from its outer atmosphere at a temperature of 8,929 K, giving it the white-hued glow of an A-type star.

In the past, radial velocity variations have been reported, but this remains unconfirmed.Template:Citation needed The star does not show any significant photometric variations and is used as a ubvy standard star. A debris disk of warm dust around this star has been detected by Spitzer Space Telescope.

Sigma Andromedae is a candidate for membership in the stream of stars associated with the Ursa Major Moving Group. This is a set of stars that share a common motion through space, which suggests they originated together.

Naming

In Chinese, Template:Lang (Template:Lang), meaning Celestial Stable, refers to an asterism consisting of σ Andromedae, θ Andromedae and ρ Andromedae. Consequently, the Chinese name for σ Andromedae itself is Template:Lang (Template:Lang, Template:Lang-en.)