Extra-galactic address for high energy particles
Science: Every so often, a subatomic particle crashes into Earth's atmosphere packing as much energy as a large hailstone. Physicists have struggled for decades to determine where such ultrahigh-energy cosmic rays come from, what they consist of, and how they are accelerated to energies 100 million times greater than particle accelerators have reached. Now answers may be in sight. Ultra-high-energy cosmic rays appear to come from the neighborhoods of certain nearby churning galaxies, physicists working with the gigantic Pierre Auger Observatory in western Argentina report in Science this week (page 938). The finding marks a first big step toward explaining the mysterious particles, say researchers to Science's Adrian Cho.
