  We are concerned with the analysis of finite time collision trajectories for
a class of singular anisotropic homogeneous potentials of degree $-\alpha$,
with $\alpha\in(0,2)$ and their lower order perturbations. It is well known
that, under reasonable generic assumptions, the asymptotic normalized
configuration converges to a central configuration. Using McGehee coordinates,
the flow can be extended to the collision manifold having central
configurations as stationary points, endowed with their stable and unstable
manifolds. We focus on the case when the asymptotic central configuration is a
global minimizer of the potential on the sphere: our main goal is to show that,
in a rather general setting, the local stable manifold coincides with that of
the initial data of minimal collision arcs. This characterisation may be
extremely useful in building complex trajectories with a broken geodesic
method. The proof takes advantage of the generalised Sundman's monotonicity
formula.
