For a stable orbit the ratio between the moon's orbital period "P"s around its primary and that of the primary around its star "P"p must be < 1/9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days. Simulations suggest that a moon with an orbital period less than about 45 to 60 days will remain safely bound to a massive giant planet or brown dwarf that orbits 1 AU from a Sun-like star. In the case of Upsilon Andromedae d, the orbital period would have to be no greater than 120 days (around 4 months) in order to have a stable orbit.