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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.

 

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Welcome to the Center for Particle and Gravitational Astrophysics!

The Center for Particle and Gravitational 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 eight major international projects which make observations using extremely high energy protons and nuclei, neutrinos, gamma-rays, X-rays and gravitational waves. These projects are, respectively, the Pierre Auger Cosmic Ray Observatory, the IceCube Neutrino Observatory, the Swift Gamma-Ray Burst Explorer satellite, the Chandra X-ray Observatory, the XMM-Newton X-ray Observatory, the Laser Interferometric Gravitational Wave Observatory (LIGO), the North American Nanohertz Observatory for Gravitational-waves (NANOGrav) and the High Altitude Water Cherenkov (HAWC) TeV gamma-ray detector.

Our faculty are also involved in developing instrumentation for future facilities such as the International X-ray Observatory, the Large Synoptic Survey Telescope (LSST) and a major ESA flagship mission, the X-ray observatory Athena. There is also ongoing work with the Fermi satellite, the VERITAS high energy gamma ray observatory, the Cosmic Ray Energetics and Mass (CREAM), including a version to deploy on the International Space Station (ISS-CREAM), the High Energy Light Isotope eXperiment (HELIX) high-altitude balloon, and in the former Laser Interferometer Space Antenna (LISA) project, now called NGO.

Penn State is one of only a small handful of U.S. institutions participating in both Auger and IceCube, the 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). Some GRBs are believed to be especially violent supernova explosions, while others are probably mergers of collapsed stars in binary systems.

The Swift GRB Explorer satellite is presently providing the best gamma ray and X-ray observations of GRB explosions. Swift has been successfully operating for a number of years, its mission control center being at Penn State. Chandra and XMM have been successfully operating for over a decade and are leading to substantial advances in understanding the demography, physics, and ecology of supermassive and stellar mass black holes, active galaxies and supernovae. The Advanced LIGO (aLIGO) gravitational wave detector has chalked up its first major success in making the first direct detection of gravitational waves, originating from 60 solar mass black hole binary system.

Commensurate with these significant experimental efforts, Penn State also plays a leading role in the theoretical and numerical modeling of fundamental high energy interactions as well as astrophysical phenomena such as black holes, gamma-ray bursts, the high energy Universe and the formation of the first objects and large scale structures in the Universe.

GRBs, and the mergers of super-massive black holes in the cores of galaxies and quasars are also likely sources of detectable gravitational waves. Our Center is engaged in observing GRBs, active galaxies, supernovae and clusters of galaxies, looking for strong-interaction protons and nuclei, weak-interaction neutrinos, electromagnetic radiation, and gravitational waves. Together we cover all four forces of nature. We have initiated and lead a specific multi-messenger observational program called the Astrophysical Multimessenger Observatory Network (AMON), which aims to utilize all four forces to detect sub-threshold signals from the above described cosmic sources. 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, the Center for Theoretical and Observational Cosmology 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.

News/Events

  • The Institute for CyberScience and the Institute for Gravitation and the Cosmos will host a three-day summer camp for Centre Region high school students to learn about the search for gravitational waves. More details on the camp can be found at http://gravity.psu.edu/events/gravwavecamp/. [Read full story…]
  • Chad Hanna, assistant professor of physics, has been honored with the inaugural Normal and Trygve Freed Early Career Professorship in Physics.
  • The second Multi-Messenger Approaches to Cosmic Rays: Origins and Space Frontiers (MACROS) Workshop was held at Penn State, June 20-22, 2016. Kohta Murase, Foteini Oikonomou and Ian Shoemaker were local organizers of the workshop which was designed for those interested in the many unsolved mysteries surrounding cosmic rays.
  • Mark Strikman, among others, is an organizer of the QCD at Cosmic Energies - VII Workshop which will be held in Chalkida, Greece, May 16-20, 2016.
  • Researchers from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory unveiled a new map of the very-high-energy sky at the APS April Meeting 2016. Penn State researchers associated with HAWC include Miguel Mostafa, Alan Foster, Kelly Malone, and John Pretz. [Read full story…]
  • Miguel Mostafá recently participated in the 2016 TedX talks and spoke about ultra high energy cosmic waves, the highest energy particles in the universe. Watch the YouTube video Catching the Fastest Particles in the Universe"
  • "New clues in the hunt for the sources of cosmic neutrinos" is the subject of a paper published in the February 18, 2016 online edition of Physical Review Letters by Kohta Murase, assistant professor of physics and astronomy and astrophysics, and colleagues. [Read full story…]
  • W. Niel Brandt has been awarded the prestigious Bruno Rossi prize, the top award given each year by the High Energy Astrophysics Division of the American Astronomical Society. Brandt is honored with the 2016 Bruno Rossi Prize for his leadership of the research effort that used NASA's Chandra X-ray Observatory to detect X-ray signals from extreme sources at vast distances from Earth. [Read full story…]
  • Doug Cowen, professor of physics and astronomy and astrophysics, and Gordana Tesic, a postdoctoral researcher in Cowen's group, are members of a team of scientists that has been recognized with the 2016 Breakthrough Prize in Fundamental Physics. [Read full story…]
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