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News from exotic sources PDF Print E-mail
Written by Daniel Marin   
Monday, 07 July 2008

Cosmic rays rain down on the Earth from space, which give us evidence of existing violent phenomena and exotic sources in the Universe such as supernovae, active galactic nuclei and pulsars. Mainly made of protons (about 90%), but also of other subatomic particles, cosmic rays have energies in a very wide range: from the less energetic ones coming from the Sun, to the most energetic from galactic and extragalactic sources.
The entire range of these energies covers at least 12 orders of magnitude. In order to reveal and study cosmic rays, various techniques are used based on particular cosmic rays’ nature and energies. They can be “captured” directly, or indirectly using the atmosphere as a detector.

X ray
• © NASA HST / CXC / ASU /
J.H ester et al •

Among the most probable sites for the production of galactic cosmic rays are the shock waves of supernova remnants. The traces of these exploding stars, expanding clouds of gas, can last for thousands of years. Bouncing back and forth in the remnants’ magnetic field, some particles can attain very high energies, sufi cient to escape their own galaxy, travel intergalactic space and be detected here on the Earth. High-energy electrons are accelerated in the shock waves of supernova remnants such as the Crab Nebula, a remnant seen in this X-ray and visible light picture.
These electrons in turn produce very high-energy gamma rays.



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