TITLE:
A restricted four-body model for the dynamics near the Lagrangian
points of the Sun-Jupiter system

AUTHORS:
Frederic Gabern and Angel Jorba
Departament de Matematica Aplicada i Analisi,
Universitat de Barcelona,
Gran Via 585, 08007 Barcelona, Spain
E-mails: gabern@mat.ub.es, angel@maia.ub.es

ABSTRACT:
We focus on the dynamics of a small particle near the Lagrangian
points of the Sun-Jupiter system. To try to account for the effect of
Saturn, we develop a specific model based on the computation of a true
solution of the planar three-body problem for Sun, Jupiter and Saturn,
close to the real motion of these three bodies. Then, we can write the
equations of motion of a fourth infinitesimal particle moving under
the attraction of these three masses. Using suitable coordinates, the
model is written as a time-dependent perturbation of the well-known
spatial Restricted Three-Body Problem.

Then, we study the dynamics of this model near the triangular points.
The tools are based on computing, up to high order, suitable normal
forms and first integrals. From these expansions, it is not difficult
to derive approximations to invariant tori (of dimensions 2, 3 and 4)
as well as bounds on the speed of diffusion on suitable domains. We
have also included some comparisons with the motion of a few
Trojan asteroids in the real Solar system.

Numerical values for the Fourier coefficients of this model have
also been included, in separate files, in a tar+gzipped file
(see the link "PostScript+additional files").
