High Energy Astrophysics

The development of the atmospheric Cherenkov imaging technique has led to significant advances in gamma-ray detection sensitivity in the energy range from 200 GeV to 50 TeV. The Whipple Observatory 10m reflector has detected the first galactic and extragalactic sources in the Northern Hemisphere; the Crab Nebula has been established as the standard candle for ground-based gamma-ray astronomy. The highly variable Active Galactic Nuclei, Markarian 421 and Markarian 501, have proved to be particularly interesting. A new generation of telescopes with improved sensitivity has the promise of interesting measurements of fundamental phenomena in physics and astrophysics. VERITAS (the Very Energetic Radiation Imaging Telescope Array System) is one such next generation system; it is an array of seven large atmospheric Cherenkov telescopes planned for a site in southern Arizona.