Cosmic rays are high-energy radiation, mainly originating outside the Solar System. Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface. Composed primarily of high-energy protons and atomic nuclei, they are of mysterious origin. Data from the Fermi space telescope (2013) have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernovae explosions of stars. Active galactic nuclei probably also produce cosmic rays. Wikipedia, Cosmic Ray
Ultra-high-energy cosmic ray:
In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray particle with a kinetic energy greater than 10^18 eV, far beyond both the rest mass and energies typical of other cosmic ray particles.
The first observation of a cosmic ray particle with an energy exceeding 1.0×10^20 eV (16 J) was made at the Volcano Ranch experiment in New Mexico in 1962.
Cosmic rays are atomic nuclei that zip through space at the highest energies observed in nature. Some unknown engine accelerates them to energies 100 million times as high as that of protons in the Large Hadron Collider, the largest particle accelerator on Earth .
The largest study yet of the most energetic particles to slam into Earth provides the first solid clues to where the particles come from. Using a giant array of tubs of water, scientists found that these ultrahigh energy cosmic rays mostly originate outside the Milky Way.
An international team analyzed about 12 years of data to show that particles with energies above 8 billion billion electron volts generally come from a particular direction in the sky, and it’s not the galaxy’s center.
Karl-Heinz Kampert of the University of Wuppertal in Germany, a spokesperson for the Pierre Auger Collaboration, which made the discovery said "It’s the first clear experimental indication that the sources of these high-energy particles are located outside of our own galaxy, probably somewhere in the nearby universe".
The observatory caught 30,000 ultrahigh energy cosmic rays between January 1, 2004, and August 31, 2016. The team found that, compared with the average density of particle strikes across the whole sky, about 6 percent fewer particles came from the center of the Milky Way. Slightly more particles came from a direction about 120 degrees away from the galactic center.
Karl-Heinz Kampert also said "Intriguingly, the excess points in the direction of the nearest cluster of galaxies to the Milky Way, located between 300 million and 900 million light-years from Earth. That finding suggests cosmic rays are produced in some galaxies, just not ours. Wikipedia, Ultra-high-energy cosmic ray
“Cosmic rays are mostly protons accelerated by some of the most energetic phenomena in the universe, like the blast waves of exploding stars and jets produced when matter falls into black holes,” explained Mazziotta.
These images show the steadily improving view of the Moon’s gamma-ray glow from NASA’s Fermi Gamma-ray Space Telescope. Each 5-by-5-degree image is centered on the Moon and shows gamma rays with energies above 31 million electron volts, or tens of millions of times that of visible light. At these energies, the Moon is actually brighter than the Sun. Brighter colors indicate greater numbers of gamma rays. This image sequence shows how longer exposure, ranging from two to 128 months (10.7 years), improved the view.