Portal:Radiation astronomy/Resource/6

Cosmic rays
The graph on the right shows an inverse correlation between sunspot numbers (solar activity) and neutron production from galactic cosmic rays.

There is "a correlation between the arrival directions of cosmic rays with energy above 6 x 1019 electron volts and the positions of active galactic nuclei (AGN) lying within ~75 megaparsecs."

The Oh-My-God particle was observed on the evening of 15 October 1991 over Dugway Proving Ground, Utah. Its observation was a shock to astrophysicists, who estimated its energy to be approximately $3 eV$ (50 joules)&mdash;in other words, a subatomic particle with kinetic energy equal to that of a baseball (142 g or 5 oz) traveling at 100 km/h (60 mph).

It was most probably a proton with a speed very close to the speed of light, so close, in fact, [(1 − $5$) &times; c], that in a year-long race between light and the cosmic ray, the ray would fall behind only 46 nanometers ($5$ light-years), or 0.15 femtoseconds ($1.5 s$).