Orbital Motion in Outer Solar System

Motion of a point mass in gravitational fields of the Sun and of the galactic disk is studied. Fundamental features of the motion are found by investigating the time-averaged differential equations for orbital evolution. Several types of possible orbits are mathematically exactly derived in a strictly analytical way. The relation $a^{3} ~ P^{2} = f (e_{0}, i_{0}, \omega_{0})$ between semimajor axis a and period P of the change of osculating orbital elements is found (the index 0 denotes initial values of the quantities). Due to conservation of energy in potential fields a is a constant. Moreover, the component of angular momentum perpendicular to the galactic plane is conserved. Due to these facts the system of equations reduces to two equations for either (e, $\omega$), or (i, $\omega$) (the length of the ascending node does not enter the equations for a, e, i, $\omega$ and is not solved here).