Upsilon Andromedae system
Upsilon Andromedae (υ Andromedae, υ And) is a binary star system with several planets. The primary star (Upsilon Andromedae A) is an F-type main-sequence star. The second star (Upsilon Andromedae B) is a red dwarf in a wide orbit around the primary.
System components
Upsilon Andromedae A is a yellow-white dwarf of spectral type F8V. The star is around 3.1 billion years old.
Upsilon Andromedae B is a red dwarf of spectral type M4.5V located at a minimum distance of 750 AU from the primary star. The B star is less massive and far less luminous than A.
Planetary system
Some simulations show that the eccentricity of the system's planets may have arisen from a close encounter between the outer planet and a fourth planet, with the result that the fourth planet was ejected from the system or destroyed. If so, the rogue planet would have had to eject immediately; it is unclear how likely this situation might be. Other models are possible. The fourth planet is in a 3:1 resonance with Upsilon Andromedae d.
Upsilon Andromedae does not appear to have a circumstellar dust disk similar to the Kuiper belt. This may be the result of perturbations from the companion star removing material from the outer regions of the Upsilon Andromedae A system.
Planets:
