Iron nuclei, not protons, appear to be the most energetic cosmic rays
JUL 02, 2009
DOI: 10.1063/PT.5.023477
Science News : Scientists have generally assumed that the most energetic cosmic rays are primarily protons. That’s true even though heavier nuclei such as iron are more easily accelerated to high energies because of their greater electric charge.Heavy nuclei, however, are also more fragile and the extraordinarily violent processes that rev them up to enormous energies can also cause these nuclei to fragment."Ask anybody what are the highest-energy [cosmic ray] particles, and they’d say âprotons,’ ” says physics Nobel laureate James W. Cronin of the University of Chicago. But, as he announced 22 June at the Windows on the Universe meeting, the Pierre Auger Observatory in Malargüe, Argentina, has identified an abundance of iron nuclei at some of the highest energies its cosmic ray detectors can record. Related Links Studies of Cosmic Ray Composition and Air Shower Structure with the Pierre Auger Observatory The Cosmic Ray Energy Spectrum and Related Measurements with the Pierre Auger Observatory
© 2009 American Institute of Physics
