  We consider autonomous Newtonian systems with Coriolis forces in two and
three dimensions and study the existence of branches of periodic orbits
emanating from equilibria. We investigate both degenerate and nondegenerate
situations. While Lyapunov's center theorem applies locally in the
nondegenerate, nonresonant context, equivariant degree theory provides a global
answer which is significant also in some degenerate cases.
  We apply our abstract results to a problem from Celestial Mechanics. More
precisely, in the three-dimensional version of the Restricted Triangular Four
Body Problem with possibly different primaries our results show the existence
of at least seven branches of periodic orbits emanating from the stationary
points.
