Gamma-ray bursts: The brightest explosions in the Universe.

A few times a day the sky is lit up by brilliant flashes of gamma-rays. Though discovered more than three decades ago, astronomers were in the dark about the origin of these bursts. The speaker will present evidence that decisively demonstrate that many gamma-ray bursts (GRB) are located at cosmological distances. These bursts are then the most brilliant astronomical objects. There are good reasons to suspect that GRBs may well be responsible for the highest energy cosmic rays in the Universe and are appearing to be attractive targets for gravitational wave interferometers, TeV and neutrino telescopes. The talk will end with a discussion of the nature of the progenitors of GRBs, namely the end state of massive stars. It has been speculated that GRBs mark the birth of spinning black holes from which the energy to fuel these brilliant bursts is somehow extracted.