  We study the energy loss of an energetic heavy quark produced in a high
temperature quark-gluon plasma and travelling a finite distance before emerging
in the vacuum. While the retardation time of purely collisional energy loss is
found to be of the order of the Debye screening length, we find that the
contributions from transition radiation and the Ter-Mikayelian effect do not
compensate, leading to a reduction of the zeroth order (in an opacity
expansion) energy loss.
