Effects of perturbing forces on the orbital stability of planetary systems

We consider dynamical effects of additional perturbative forces due to the non-point-mass nature of stars and planets: effects such as quadrupolar dis tortion and tidal friction in the systems of exoplanets. It is shown that o ne should not neglect these forces while modeling the dynamics of planetary systems, especially taking into account the undefined real masses of the p lanets due to unknown orbital inclinations and the unsatisfactory applicati on of Keplerian fits to the radial velocity data in multiple planetary syst ems.