Finding The Origin Of Cosmic Rays: Scientists Unearth New Details

on September 02 2013 8:40 AM
cosmic rays
Researchers have found new details about the cosmic rays in the universe, which can help determine the origin of the high-energy particles. NASA

Scientists have found new information that takes the quest for the origin of cosmic rays in the universe one step closer to the answer, and hope that the latest discovery may help solve the mystery of exactly how and where these rays, which are actually high-energy particles, are created.

Scientists at the University of Delaware conducted a study by using data from the IceCube Neutrino Observatory located at the South Pole, and found that cosmic rays, which are known to reach energies above 100 billion giga-electron volts, or GeV, can be found in the 1.6 times 10^6 GeV to 10^9 GeV range. The study, published in the journal, Physical Review D, said that scientists are interested in identifying cosmic rays in this range, because the transition from cosmic rays produced in the Milky Way Galaxy to “extragalactic” cosmic rays, which are produced outside our galaxy, are expected to occur in this energy range.

“The more scientists learn about the energy spectrum and chemical composition of cosmic rays, the closer humanity will come to uncovering where these energetic particles originate,” a university statement said.

According to scientists, cosmic rays can damage electronics on Earth. They can also harm human DNA, which puts astronauts in space especially at risk. Exploding stars called supernovae are among the sources of cosmic rays in the Milky Way, while distant objects such as collapsing huge stars and active galactic nuclei far from the Milky Way also produce the highest-energy particles.

According to Bakhtiyar Ruzybayev, a physicist at the University of Delaware, the cosmic-ray energy spectrum does not follow a power law between the “knee” around 4 PeV (peta-electron volts) and the “ankle” around 4 EeV (exa-electron volts), as previously thought, but shows 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.”

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