G.T. Zatsepin and birth of gamma-ray astronomy
Institute for Nuclear Research, Russian Academy of Sciences, prosp. 60-letiya Oktyabrya 7a, Moscow, 117312, Russian Federation
The centenary of G.T. Zatsepin, a well-recognized authority in cosmic ray physics and nuclear and neutrino astrophysics, offers an opportunity both to retrospect the work he is well-known for and to take a look at some of his lesser known ideas, even to specialists. One example is his pioneering proposal to employ the Cherenkov emission from electromagnetic cascades in the upper atmosphere as a tool to search for local gamma-ray sources on the celestial sphere. First published by G.T. Zatsepin and A.E. Chudakov in 1961, the idea was immediately put into practice by the latter in constructing the world's first gamma-ray telescope in Crimea. Zatsepin and Chudakov's method is still today the basis for very high energy gamma-ray astronomy, with the number of discovered sources approaching two hundred. New grandiose projects that are currently underway in this rapidly developing field of astronomy hold promise for an order of magnitude increase in the sensitivity of the method.