Supernovae are among the sources of high-energy particles here in the Milky Way.
Science Recorder | James Fluere | Sunday, September 01, 2013
The mystery of cosmic ray origins may soon be solved, according to researchers at the University of Delaware. It’s a problem that has stumped researchers for years, but a new study utilizing data from the IceCube Neutrino Observatory at the South Pole offers information that may help solve the mystery of exactly how and where these high-energy particles are created.
The more researchers discover about the energy spectrum and chemical structure of cosmic rays, the closer they will come to determining where these mysterious particles come from.
According to a news release from the University of Delaware, cosmic rays are capable of achieving energies greater than 100 billion giga-electron volts. The data gathered by IceTop, the IceCube Observatory’s surface array of detectors, cover the energy interval from 1.6 times 106 GeV to 109 GeV.
Researchers are particularly curious about cosmic rays in this range because the change from cosmic rays created in the Milky Way Galaxy to cosmic rays generated outside our galaxy is predicted to take place in this energy interval.
Supernovae are among the sources of high-energy particles here in the Milky Way, while far-off objects like collapsing massive stars and active galactic nuclei are thought to generate the highest energy particles in nature.
According University of Delaware physicist Bakhtiyar Ruzybayev, the cosmic-ray energy spectrum does not abide by a simple power law between the “knee” around 4 PeV and the “ankle” around 4 EeV. Instead, the cosmic-ray energy spectrum reveals features like hardening around 20 PeV and steepening around 130 PeV.
“The spectrum steepens at the ‘knee,’ which is generally interpreted as the beginning of the end of the galactic population. Below the knee, cosmic rays are galactic in origin, while above that energy, particles from more distant regions in our universe become more and more likely,” Ruzybayev said. “These measurements provide new constraints that must be satisfied by any models that try to explain the acceleration and propagation of cosmic rays.”
The study’s results are discussed in the journal Physical Review D.
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