Mystery solved: Super-energetic space particles crash to Earth from far away

September 21, 2017

UNIVERSITY PARK, Pa. — Super-energetic space particles, which were thought to have been blasted toward Earth from somewhere outside our solar system, now have been discovered to be from very far away indeed — from far outside our Milky Way galaxy. The discovery was made by an international team that includes Penn State scientists and the Pierre Auger Collaboration, using the largest cosmic-ray instrument ever built, the Pierre Auger Observatory in Argentina. A paper describing the discovery will be published in the journal Science on Sept. 22.

Auger Animation 9-2017

This animation illustrates the long journey of high-energy cosmic waves from the time they are shot into space from powerful events in galaxies far away from our Milky Way Galaxy until they eventually crash on Earth, leaving clues among the large array of cosmic-ray detectors in western Argentina, the Pierre Auger Observatory. Penn State scientists are members of the Pierre Auger Consortium.

Pierre Auger Collaboration

"After more than a century since cosmic rays were first detected, this is the first truly significant result from our analysis of the detections, which now have revealed the distant origin of these ultra-high-energy cosmic rays," said Miguel Mostafá at Penn State. He and Stephane Coutu — both professors of physics and of astronomy and astrophysics and Fellows of the American Physical Society — lead teams of students and post-doctoral scientists in research at Penn State's Pierre Auger Collaboration group. "Now we know that the highest-energy particles in the universe came from other galaxies in our cosmological neighborhood," Mostafá said.

Mostafá and Coutu have been working on the project since 1996 and 1997, respectively, with support from the U.S. National Science Foundation. Mostafá has been a coordinator of the Auger team in charge of this analysis of cosmic-ray arrival directions, and is one of the corresponding authors on the Science article.

Although the Pierre Auger Collaboration's discovery clearly shows an origin outside our Milky Way galaxy, the specific sources that are producing the particles have not yet been discovered. "We are now considerably closer to solving the mystery of where and how these extraordinary particles are produced, a question of great interest to astrophysicists," said Karl-Heinz Kampert, professor of physics at the University of Wuppertal in Germany and spokesperson for the Pierre Auger Collaboration.

  • Three students from Miguel Mostafá's lab, standing in front of the 1600th detector installed as a component of the large Pierre Auger Observatory array in western Argentina.

    Graduate students from Miguel Mostafá's lab visiting the 1600th detector of the large Pierre Auger Observatory array in western Argentina.

    IMAGE: Miguel Mostafá lab, Penn State University
  • One of the many many detectors in the very large Pierre Auger Cosmic Ray Observatory array in Artentina

    One of the many many detectors in the very large Pierre Auger Cosmic Ray Observatory array in Argentina.

    IMAGE: The Pierre Auger Observatory
  • One of the four small white buildings housing the flourescence detectors of the Pierre Auger Observatory in Argentina.

    One of the four fluorescence-detector buildings that are components of the Pierre Auger Observatory in western Argentina. The fluorescence detectors measure the faint ultraviolet light emitted by cosmic-ray air showers streaking through the atmosphere. These detectors are one of the two types of complementary detection devices used at the observatory. Comparing results from the different types of detectors helps scientists produce the most accurate results about the energy of the primary cosmic rays that reach our planet Earth. Find more information at https://www.auger.org/index.php/observatory/auger-hybrid-detector

    IMAGE: The Pierre Auger Observatory
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Last Updated December 21, 2017