  We find that free-floating planets can remain bound to a star cluster for
much longer than was previously assumed: of the order of the cluster half-mass
relaxation timescale as opposed to the crossing-time. This result is based on
N-body simulations performed with the new GRAPE-6 special purpose hardware and
is important in the context of the preliminary detection of a population of
free-floating sub-stellar objects in the globular cluster M22. The planets in
our N-body study are of Jupiter mass and are initially placed in circular
orbits of between 0.05 and 50 AU about a parent star whose mass is chosen from
a realistic initial mass function. The presence of the free-floating planets is
the result of dynamical encounters between planetary systems and the cluster
stars. Most planets are liberated from their parent star in, or near, the
cluster core, and then drift outwards on a timescale of ~ 10^{8-9} year. This
still implies the existence of many (~100) planets per star if the M22 result
is confirmed.
