Cosmic Rays and Galactic Nuclei

The Pierre Auger Collaboration has found evidence that the highest energy cosmic rays are produced by active galactic nuclei. This international collaboration of physicists announced in the cover story of the November 9th (2007) issue of Science Magazine that they observe a statistically significant correlation between the arrival directions of the highest energy cosmic rays and positions of these objects that are less than 240 million light years from Earth. Active galactic nuclei are believed to be supermassive black holes that are consuming gas and dust at the centers of some galaxies. The correlation is based on 27 particles, with energy in excess of 10 Joules each, which were recorded while the observatory was being constructed in Argentina. The array of detectors in Argentina has now reached its full size of 3000 square kilometers, and a northern site for the Auger Observatory is planned for southeast Colorado. The Penn State team involved in this project include Sanjeevi Atulugama, Jose Bellido, Stephane Coutu, Adrienne Criss, Michael Roberts and Paul Sommers. Paul Sommers was also elected co-spokesperson for the Pierre Auger Collaboration beginning in November 2007.