A distant stellar companion in the ν Andromedae system

Upsilon Andromedae is an F8 V star known to have an extrasolar system of at least three planets in orbit around it. Here we report the discovery of a low-mass stellar companion to this system. The companion shares common proper motion, lies at a projected separation of similar to750 AU, and has a spectral type of M4.5 V. The effect of this star on the radial velocity of the brighter primary is negligible, but this system provides an interesting test bed for stellar planetary formation theory and understanding dynamical stability since it is the first multiple planetary system known in a multiple stellar system.