The classical disturbing function of the three-body problem widely used in planetary dynamics studies is an expansion of the gravitational interaction of the three-body problem with respect to zero eccentricity and zero inclination. This restricts its validity to nearly coplanar orbits. Motivated by the dynamical study of asteroids, Centaurs and transneptunian objects with arbitrary inclinations, we derive a series expansion of the gravitational interaction with respect to an arbitrary reference inclination that generalises our work on the polar and retrograde disturbing functions. The new disturbing function, like the polar one, may model any resonance as expansion order is unrelated to resonance order. The powers of eccentricity and inclination of the force amplitude of a $p$:$q$ resonance depend only on the parity of the resonance order $|p-q|$. Disturbing functions with non zero reference inclinations are thus physically different from the classical disturbing function as the former are based on the three-dimensional three-body problem and the latter on the two-dimensional one. We illustrate the use of the new disturbing function by showing that what is known as pure eccentricity resonances are intrinsically dependent on inclination contrary to the prediction of the classical disturbing function. We determine the inclination dependence of the resonance widths of the 2:1 and 3:1 prograde and retrograde inner resonances with Jupiter as well as those of the asymmetric librations of the 1:2 and 1:3 prograde outer resonances with Neptune.
F. Namouni and M. Morais
Thu, 12 Oct 17
Comments: 22 pages, 4 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society