System Components
Upsilon Andromedae A is a yellow-white dwarf of spectral type F8V, similar to the Sun, but younger, more massive, and more luminous. According to its entry in the Geneva–Copenhagen survey, the star is around 3.1 billion years old, and has a similar proportion of iron relative to hydrogen to the Sun. At around 1.3 solar masses, it will have a shorter lifetime than the Sun. The amount of ultraviolet radiation received by any planets in the star's habitable zone would be similar to the ultraviolet flux the Earth receives from the Sun.
Upsilon Andromedae B is a red dwarf of spectral type M4.5V located at a distance (in the plane of the sky) of 750 AU from the primary star. The true separation between the two stars is unknown because the displacement along the line of sight between us and the Upsilon Andromedae stars is unknown, so this value is a minimum separation. It was discovered in 2002 in data collected as part of the Two Micron All Sky Survey. The star is less massive and far less luminous than the Sun.
The Washington Double Star Catalog lists two optical components; however, these do not share the system's proper motion and only appear close to Upsilon Andromedae because they happen to lie near the same line of sight.
Read more about this topic: Upsilon Andromedae
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