Institut de recherche sur les lois fondamentales de l'Univers

Cosmic Rays were discovered in the early 1910s. Since then, their origin remains a mystery: sources can't be directly observed as their trajectory is scrambled by the galactic magnetic fields. At ultra high energies, however, their sources should become observable. The Pierre Auger Observatory detects cosmic rays at these energies by covering an area of 3000 km^2 in the south of Argentina. After the first 3 years of operation Auger found strong indications that Ultra High Energy Cosmic Rays come from nearby, extragalactic sources, hinting at the solution of a century old problem and opening a window for charged particle astronomy. In this seminar, I will describe the Pierre Auger Observatory and its astrophysical context, its most recent results and the exciting prospects for the near future.