Monday, September 25, 2017


 Researchers using the Pierre Auger Observatory in Argentina have discovered that the highest-energy cosmic rays that bombard Earth actually come from galaxies far, far away.
 Cosmic rays are atomic nuclei of elements ranging from hydrogen to iron that zip through outer space near the speed of light. The sun emits relatively low-energy cosmic rays, but since over 50 years ago, scientists have also been detecting ultra-high-energy cosmic rays more powerful than those produced by particle accelerators hitting Earth.
 In order to discover the origins of these cosmic rays, scientists looked for the calling card of these rays: sprays of electrons, photons and other particle that are produced when cosmic rays hit the top of Earth's atmosphere. Using data collected from between 2004 and 2016 by the Pierre Auger Observatory, it was found that most high-energy cosmic rays originated from a broad area of sky about 90 degrees away from the direction of the Milky Way's core.
 This direction is a place "with an increased density of nearby galaxies," said Karl-Heinz Kampert, an astrophysicist at the University of Wuppertal in Germany. "These galaxies, or some subset of these galaxies, contain the sources of these cosmic rays."
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Image Credit: Credit: A. Chantelauze/S. Staffi/L. Bret

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