The Origin of Cosmic Rays in the Universe: One Step Closer

First Posted: Aug 30, 2013 01:41 PM EDT

The origin of cosmic rays in the universe has puzzled scientists for decades. Now, though, they may be one step closer to having their answer. Using data from the IceCube Neutrino Observatory at the South Pole, researchers have discovered new information that may lead to the discovery of where cosmic rays come from.

Cosmic rays are high energy particles in space. Directed toward Earth, they can damage electronics. They can also impact human DNA, putting astronauts in space at risk. As agencies develop long-term missions into the cosmos, it's more important than ever to understand how to counter these rays.

In order to find out a little bit more about these cosmic rays, the researchers covered the energy range of rays from 1.6 times 10^6 GeV and 10^9 GeV. They were particularly interested in identifying rays in this interval since the transition from cosmic rays produced in the Milky Way to "extragalactic" cosmic rays is expected to occur in this range.

So what did they find? It turns out that the cosmic ray energy spectrum does not follow a simple power law between the "knee" (around 4 PeV) and the "ankle" (around 4 EeV) as previously thought. Instead, this spectrum exhibits 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," said Ruzybayev, one of the researchers, in a news release. "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. These measurements provide new constraints that must be satisfied by any models that try to explain the acceleration and propagation of cosmic rays."

The findings could eventually lead to the discovery of where these cosmic rays originate. In addition, they reveal a little bit more about the universe we live in.

The research is published in the journal Physical Review D.

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