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Planetary orbital equations in externally-perturbed systems: position and velocity-dependent forces

Dimitri Veras
N. Wyn Evans
Journal / Anthology

Celest Mech Dyn Astr
Year: 2013
Volume: 115
Page range: 123–141

The increasing number and variety of extrasolar planets illustrates the importance of characterizing planetary perturbations. Planetary orbits are typically described by physically intuitive orbital elements. Here, we explicitly express the equations of motion of the unaveraged perturbed two-body problem in terms of planetary orbital elements by using a generalized form of Gauss’ equations. We consider a varied set of position and velocitydependent perturbations, and also derive relevant specific cases of the equations: when they are averaged over fast variables (the “adiabatic” approximation), and in the prograde and retrograde planar cases. In each instance, we delineate the properties of the equations. As brief demonstrations of potential applications, we consider the effect of Galactic tides. We measure the effect on the widest-known exoplanet orbit, Sedna-like objects, and distant scattered disk objects, particularly with regard to where the adiabatic approximation breaks down. The Mathematica code which can help derive the equations of motion for a user-defined perturbation is freely available upon request.

*Applied Mathematics
*Applied Mathematics > Computer Science

Perturbation methods, Computer methods, Planetary systems, Comets and meteors, Adiabatic approximation, Galactic tides