Werner Hofmann, Director and Scientific Member, Max Planck Institute for Nuclear Physics, Heidelberg, Germany
Over the last decade, very high energy (VHE) gamma ray astronomy - at photon energies of 100 GeV and beyond - has developed in giant steps, with the number of known cosmic VHE gamma ray sources approaching 200. Systems of large imaging atmospheric Cherenkov telescopes have played a key role in this development. VHE gamma rays cannot be produced in thermal processes but are produced by interactions of high energy particles. Gamma rays trace populations of such particles and enable the cosmic particle accelerators to be imaged. VHE gamma ray emitters are ubiquitous in the Galaxy and beyond; they include supernova remnants, pulsars and pulsar wind nebulae and binary systems, as well as starburst galaxies, radio galaxies and blazars. This presentation will briefly introduce the Cherenkov technique and then discuss some of the key results, concentrating mostly on sources in our Galaxy, as observed with the H.E.S.S. telescopes. This talk will conclude with an outlook towards the Cherenkov Telescope Array CTA, as the next-generation facility for ground-based gamma-ray astronomy.