Black holes and neutron stars are responsible for remarkably powerful outbursts spanning a large range of energies and timescales. The recent outburst from the magnetar explosion associated with SGR 1806-20 released 1038 Joules of energy with a rise time of 300μs. Quasars, by contrast can release more than 1055 Joules over hundreds of millions years.
Many of these phenomena are intrinsically relativistic and plasma is observed to move with speeds close to that if light. It is widely believe that electromagnetic field is involved in the powering of these sources, though our understanding of fundamental mechanisms involved remains sketchy and the pathways followed by the power is still controversial. In this talk, I will summarize recent observations of relativistic explosions and make the case that the energy is transported essentially electromagnetically. Particular attention will be given to the description of magnetars, blazar jets and radio pulsars.