VERITAS
Very Energetic Radiation Imaging Telescope Array System
VERITAS Collaboration
The technique used to detect very high energy gamma rays was pioneered at the Smithsonian's Whipple Observatory using the 10-meter optical reflector built in 1968. Very high energy gamma rays (photons with energy more than a million times the energy of a photon of visible light) interact with the upper atmosphere and initiate a cascade or shower of particles. The showers lead to a short burst of blue light. Using arrays of fast photo-detectors at the focus of the large optical reflector the Whipple group recorded the image of the cascade of particles and showed that they could identify those initiated by gamma rays from the much more numerous background produced by charged cosmic rays. Using this technique the Whipple group, with their collaborators, detected the first source of TeV gamma-rays in the Galaxy in 1989 (the Crab Nebula, a supernova remnant) and the first extragalactic source in 1992 (Markarian 421, an active galactic nucleus or quasar). Since that time a number of overseas observatories have adopted the Whipple technique and more than a dozen sources have been established. VERITAS will have a sensitivity that exceeds that of the existing Whipple telescope by a factor of ten and it is anticipated that more than a hundred sources will be detected. The scientific objectives of the project include the study of pulsars, supernova remnants, x-ray binaries, black holes, active galactic nuclei, and gamma-ray bursts. These cosmic particle accelerators may make possible the investigation of new physics at extreme energies which are only just matched on Earth by giant particle accelerators.
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