Faculty

• Stephane Coutu
• Douglas Cowen
• Tyce DeYoung
• Derek B. Fox
• Peter Mészáros (Director)
• Irina Mocioiu
• Paul Sommers
• Mark Strikman

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.

View All Research Highlights

The Center for Particle Astrophysics is engaged in a bold synergistic approach to understanding high energy processes in the universe. Our faculty at Penn State are prominent participants in three major international projects which make observations using extremely high energy protons, neutrinos and gamma-rays. These projects are, respectively, the Pierre Auger Cosmic Ray Observatory, the IceCube Neutrino Observatory and the Swift Gamma-Ray Burst Explorer satellite. Both Auger and IceCube are in advanced stages of construction and are poised to make major discoveries in the next few years. Penn State is the only U.S. institution participating in both of these premier ground-based projects of high energy particle astrophysics. Potentially observable sources for both Auger and IceCube include super-massive black holes at the center of active galaxies, and the explosive phenomena that give rise to gamma ray bursts (GRBs). These are believed to be especially violent supernova explosions and also mergers of collapsed stars in binary systems. Swift is presently providing the best gamma ray and X-ray observations of GRB explosions. Swift has been successfully operating for over three years, its mission control center being at Penn State. Penn State also plays a leading role in theoretical modeling of these explosions.

GRBs, and the mergers of super-massive black holes in the core of galaxies and quasars are also likely sources of detectable gravitational waves. Together with the Center for Gravitational Wave Physics, our Center will be studying GRBs and active galaxies by observing strong-interaction protons, weak-interaction neutrinos, electromagnetic gamma rays, and gravitational waves. Together, we cover all four forces of nature. This multi-force approach to high energy astrophysics is a pioneering venture in which the one-dimensional electromagnetic spectrum of conventional astronomy is supplemented with three other windows to the Universe. The discovery potential is enormous. Together with the Center for Fundamental Theory and the Institute for Gravitation and the Cosmos, the synergy between our various specialties and the breadth of knowledge to be gained through collaborations provide exciting prospects for making breakthroughs in our understanding of the Cosmos.