On the stability of test particles in extrasolar multiple planet systems

ABSTRACT

We have studied the dynamical evolution of test particles in the planetary systems of υ Andromedae, GJ 876, 47 UMa and 55 Cnc. Using recent radial velocity data of these stars and also utilizing a relatively new radial velocity fitting routine, we have obtained the orbital parameters of the giant planets of these systems, and studied the possibility of their harbouring of terrestrial-class planets and smaller objects. Our results indicate that, unlike the stable orbit of the newly discovered Earth-like planet of GJ 876, the orbit of the recently announced planet of 55 Cnc is unstable. Our simulations also show that the outer planet of 47 UMa may contain Trojan-type asteroids. We present the results of our detailed study of the orbital stability and dynamical behaviour of test particles throughout these systems, and investigate the possibility of stable orbits in their habitable zones. Within the context of the latter, it seems that the two systems of 47 UMa and 55 Cnc are still the only ones with the capability of harbouring habitable planets, although the new influence zones of their giant planets have caused their habitable regions to be different from the ones reported in the literature.