Gamma ray photons provide the means to study gHigh Energy Objects h, most violent phenomena in the present Universe as examples shown in Figure 1, where protons and electrons are accelerated to energies much higher than available by man-made accelerators. The ground-based technique has opened a window of seeing very high energy gamma rays in the region by about two decades of energy exceeding that of satellite detection. Figure 3 demonstrates the recent rapid growth of gamma-ray astronomy. The energy budget and expense of high energy processes in the Universe are uncovered by utilizing the very high energy gamma-ray window.
Supernova explosions impart enormous energy into surrounding matter via shock fronts.
As a result, matter are accelerated to TeV energies. Compact objects left over after supernova explosions have extremely high magnetic fields and rotation rate. In the case of young pulsars, we see in Figure 5 that a major part of the gspindown energy h available from pulsars is output in the form of gamma-rays. Active galaxies contain tightly beamed jets, along which matter becomes ultra relativistic. Enormous spatial densities of energy are expected near compact objects like black holes and neutron stars.