Researchers have discovered that super-energetic space particles crash toward Earth from far outside the Milky Way, and this challenges a previous suggestion that they came from much closer.
“Now we know that the highest-energy particles in the universe came from other galaxies in our cosmological neighborhood…”
The discovery was made using the largest cosmic-ray instrument ever built, the Pierre Auger Observatory in Argentina.
“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,” says Miguel Mostafá, a professor of physics and of astronomy and astrophysics at Penn State.
“Now we know that the highest-energy particles in the universe came from other galaxies in our cosmological neighborhood,” Mostafá says.
Mostafá and colleague Stephane Coutu have been working on the project since 1996 and 1997, respectively, with support from the US 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,” says Karl-Heinz Kampert, professor of physics at the University of Wuppertal in Germany and spokesperson for the Pierre Auger Collaboration.