Ground-Based Gamma Ray Astronomy: With the Cherenkov telescope systems VERITAS near Tucson, Arizona, and HESS in Namibia, sources of 100 GeV - 10 TeV gamma rays are observed in the northern and southern sky. Both are very sensitive instruments capable to discover many new sources in the coming years. HESS has already discovered about 50 new sources on the southern sky. VERITAS became just operational (2007). The higher sensitivity allows detection of faint sources, study of extended objects and time-resolved observations of variable emitters. Sources of gamma rays are supernova remnants, pulsar wind nebulae, X-ray binary system, colliding winds, active galactic nuclei (powered by a black hole) and others. Actually, many stages in the life of massive stars can be observed in the light of gamma rays.
The mechanisms of gamma ray production in these objects are still under investigation. Specifically, gammas from pi-0 decay which are tell-tale signs of cosmic ray acceleration have so far not been detected convincingly. TeV observations give valuable complementary information to the measurements at lower energies. Competing experiments are MAGIC, CANGAROO, Tibet AS Gamma, Argo YBJ, and Milagro.
CTA is a next generation ground based gamma ray experiment with vastly improved sensitivity and performance. It will consist of about 100 telescopes of 3 sizes (~5 m to 23 m diameter) and involve scientists from 26 countries. It the main experiment in Astroparticle Physics in the next decade worldwide.
The UK is a leading partner in this €200M project.
See here for a detailed project description:
CTA
KASCADE
