  Hot spots (HSs) are regions of enhanced radio emission produced by supersonic
jets at the tip of the radio lobes of powerful radiosources. Obtained with the
Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C445 show
bright knots embedded in diffuse optical emission distributed along the post
shock region created by the impact of the jet into the intergalactic medium.
  The observations reported here confirm that relativistic electrons are
accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the
diffuse emission tracing the rims of the front shock and the multiple knots
demonstrate the presence of additional continuous re-acceleration processes of
electrons (Fermi-II).
