James Cronin

The Highest Energy Cosmic Rays

Wednesday, 2 July 2008
09:00 - 09:30 hrs CEST


In 1938 cosmic rays with energies in excess of 1 PeV were discovered by the French physicist Pierre Auger. In 1963 a cosmic ray with energy about 100 EeV was discovered. One hundred Eev is 16 joules of energy. There is no clear understanding how astrophysical objects can accelerate protons or nuclei to such high energies, a macroscopic energy in a microscopic particle. To try to answer this question an international collaboration of 16 countries has built a large Observatory in Argentina. The detector covers an area of 3000 square kilometers. The Pierre Auger Observatory has been operating since Jan 1, 2004. The first results have revealed at the highest energies a large anisotropy. There is some evidence that the cosmic rays come from nearby ( < 50 Mpc ) extragalactic matter.

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