  Using gauge/gravity duality, we compute the energy density and angular
distribution of the power radiated by a quark undergoing circular motion in
strongly coupled ${\cal N}=4$ supersymmetric Yang-Mills (SYM) theory. We
compare the strong coupling results to those at weak coupling, and find the
same angular distribution of radiated power, up to an overall prefactor. In
both regimes, the angular distribution is in fact similar to that of
synchrotron radiation produced by an electron in circular motion in classical
electrodynamics: the quark emits radiation in a narrow beam along its velocity
vector with a characteristic opening angle $\alpha \sim 1/\gamma$. To an
observer far away from the quark, the emitted radiation appears as a short
periodic burst, just like the light from a lighthouse does to a ship at sea.
Our strong coupling results are valid for any strongly coupled conformal field
theory with a dual classical gravity description.
