It is customary to consider only ``subluminal'' light sources, or sources moving with a velocity $v$ lower than the velocity of light in vacuum $(c)$. It is assumed in this connection that the Vavilov--Cerenkov effect and the anomalous Doppler effect are possible only in media and waves for which the refractive index $n(\omega)>1$. For this reason, the phase velocity of the waves is $c_{ph}=[c/n(\omega)]c_{ph}$. Yet, as is well known, there exist also ``superluminal'' sources, with velocity $v>c$. Examples are light spots produced on a remote screen by a rotating source of light or particles. The spot velocity is $v=\Omega R$, where $\Omega$ is the angular velocity of source rotation and $R$ is the distance to the screen. The condition $v>c$ can be realized on the Earth, and is practically always realized under astronomical conditions for pulsar radiation. It is emphasized in the article that superluminal sources are equivalent in a wide range to subluminal ones, and, concretely, can generate Cerenkov radiation in vacuum and in a medium with $n(\omega)