  We use the AdS/CFT correspondence to determine the rate of energy loss of a
heavy quark moving through N=4 SU(N_c) supersymmetric Yang-Mills plasma at
large 't Hooft coupling. Using the dual description of the quark as a classical
string ending on a D7-brane, we use a complementary combination of analytic and
numerical techniques to determine the friction coefficient as a function of
quark mass. Provided strongly coupled N=4 Yang-Mills plasma is a good model for
hot, strongly coupled QCD, our results may be relevant for charm and bottom
physics at RHIC.
