UNIVERSITY PARK, Pa. — The cosmic sources of nine extremely high-energy gamma rays have been identified by members of the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory collaboration, including Penn State scientists. All of the sources identified produce gamma rays with energies over 56 trillion electron volts (TeV) and three emit gamma rays extending to 100 TeV and beyond, making these the highest-energy sources ever observed in our galaxy.
These sources constitute a new catalog that will help explain where the particles that produce high-energy gamma rays originate and how they are accelerated to such extreme velocities. It may also provide important insight into the origins of cosmic rays — high energy particles that rain down on Earth’s atmosphere and may cause electronic problems in satellites and other machinery.
“The Earth is constantly being bombarded with charged particles called cosmic rays, but because they are charged, they bend in magnetic fields and don’t point back to their sources,” said Kelly Malone, an astrophysicist in the Neutron Science and Technology group at Los Alamos National Laboratory and a member of the HAWC scientific collaboration. “We rely on gamma rays, which are produced close to the sources of the cosmic rays, to narrow down their origins.”
Malone developed a new method to determine the energy of gamma rays on an event-by-event basis as part of her doctoral research at Penn State under the supervision of Miguel Mostafá, professor of physics and of astronomy and astrophysics and a member of the HAWC collaboration. The method takes advantage of improved techniques developed and implemented by the Penn State HAWC group to reconstruct cosmic events and reject background detections that are not part of the focal event.
The results are described in a paper that appeared online January 15 in the journal Physical Review Letters.