Dynamics of self-gravitating systems : Variations on a theme by Michel
  Henon
  In this contribution to the volume in memoriam of Michel Henon, we thought
appropriate to look at his early scientific work devoted to the dynamics of
large assemblies of interacting masses. He predicted in his PhD thesis that, in
such a system, first a collapse of mass occurs at the center and that later
binaries stars are formed there. Henceforth, the negative energy of binding of
pairs becomes a source of positive energy for the rest of the cluster which
evaporate because of that. We examine under what conditions such a singularity
can occur, and what could happen afterwards. We hope to show that this
fascinating problem of evolution of self-gravitating clusters keeps its
interest after the many years passed since Henon thesis, and is still worth
discussing now.
