  We consider here the decay of unstable particles in geodesic circular motion
around compact objects. For the neutron, in particular, strong and weak decay
are calculated by means of a semiclassical approach. Noticeable effects are
expected to occur as one approaches the photonic circular orbit of realistic
black-holes. We argue that, in such a limit,the quasi-thermal spectrum inherent
to extremely relativistic observers in circular motion plays a role similar to
the Unruh radiation for uniformly accelerated observers.
