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World's largest air shower array now on track of super-high-
energy cosmic-rays Pierre Auger Observatory seeks source of
highest-energy extraterrestrial particles Batavia, Ill.- With
the completion of its hundredth surface detector, the Pierre
Auger Observatory, under construction in Argentina, this week
became the largest cosmic-ray air shower array in the world.
Managed by scientists at the Department of Energy's Fermi
National Accelerator Laboratory, the Pierre Auger project so far
encompasses a 70-square-mile array of detectors that are
tracking the most violent-and perhaps most puzzling- processes
in the entire universe. Cosmic rays are extraterrestrial
particles-usually protons or heavier ions-that hit the Earth's
atmosphere and create cascades of secondary particles. While
cosmic rays approach the earth at a range of en