STABILITY OF UPSILON ANDROMEDAE'S PLANETARY SYSTEM

Jack J. Lissauer, Eugenio Rivera

The objectives of this project are to study the dynamical properties of planetary systems that are consistent with the observational data on the three-planet system orbiting the nearby main sequence star Upsilon Andromedae. We find that systems with the planetary masses and orbital parameters that provide the best fit to stellar radial velocity observations made at Lick observatory through either February 2000 or July 2000 are substantially more stable than systems with the parameters originally announced in April 1999. Simulations using the February 2000 parameters are stable for planetary masses as much as four times as large as the observational lower bounds (which are obtained by assuming that the Solar System lies in the orbital plane of the Upsilon Andromedae planetary system). In relatively stable systems, test particles (which can be thought of as representing asteroids or Earth-like planets that are too small to have been detected to date) can survive for long times between the inner and middle planets as well as several astronomical units or more exterior to the outer planet, but we could find no stable orbits between the middle and outer planets.