A Hotspot for Powerful Cosmic Rays

Physicists a Step Closer to Finding Mysterious Sources

July 8, 2014 – An observatory run by the University of Utah found a “hotspot” beneath the Big Dipper emitting a disproportionate number of the highest-energy cosmic rays. The discovery moves physics another step toward identifying the mysterious sources of the most energetic particles in the universe.

University of Utah physicists Gordon Thomson, Charlie Jui and John Matthews discuss the Telescope Array cosmic ray observatory’s discovery of a “hotspot” – located beneath the Big Dipper in the northern sky – emitting an unusual number of ultrahigh-energy cosmic rays. The source of these rays, which are the most energetic particles in the universe, remains unknown, but the new finding will help narrow the search. Photo Credit: Lee J. Siegel, University of Utah

“This puts us closer to finding out the sources – but no cigar yet,” says University of Utah physicist Gordon Thomson, spokesman and co-principal investigator for the $25 million Telescope Array cosmic ray observatory west of Delta, Utah. It is the Northern Hemisphere’s largest cosmic ray detector.

“All we see is a blob in the sky, and inside this blob there is all sorts of stuff – various types of objects – that could be the source” of the powerful cosmic rays, he adds. “Now we know where to look.”

A new study identifying a hotspot in the northern sky for ultrahigh-energy cosmic rays has been accepted for publication by Astrophysical Journal Letters.

Thomson says many astrophysicists suspect ultrahigh-energy cosmic rays are generated by active galactic nuclei, or AGNs, in which material is sucked into a supermassive black hole at the center of galaxy, while other material is spewed away in a beam-like jet known as a blazar. Another popular possibility is that the highest-energy cosmic rays come from some supernovas (exploding stars) that emit gamma rays bursts.

Lower-energy cosmic rays come from the sun, other stars and exploding stars, but the source or sources of the most energetic cosmic rays has been a decades-long mystery.

The study was conducted by 125 researchers in the Telescope Array project, including Thomson and 31 other University of Utah physicists, plus 94 other scientists from the University of Tokyo and 28 other research institutions in Japan, the United States, South Korea, Russia and Belgium.

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