Detecting Gamma Rays

Telescopes of the VERITAS (Very Energetic Radiation Imaging Telescope Array System) gamma-ray observatory are photographed against the stars of constellation Leo. Located on the Mount Graham of Arizona, in the Whipple Observatory, The array consists of four 12m optical reflectors for gamma-ray astronomy. Since the cosmic gamma-rays are blocked by the atmosphere, astrononers detect either by space telescope and through detection of secondary particles and radiation caused by their interaction with the atmosphere. The VERITAS telescopes detect Cherenkov radiation to study the gamma-rays. When high-energy particles or strong cosmic gamma-rays interacts with the Earth’s atmosphere, it may produce electron-positron pairs with enormous velocities. Cherenkov radiation is a very faint light created when charged particles (such as an electron) passes through a medium like the atmosphere at a constant speed greater than the speed of light in that medium. The Cherenkov radiation from these charged particles is used to determine the source and intensity of the original cosmic radiation.