Discovering the Origin of Cosmic Radiation

The Earth’s atmosphere is being steadily bombarded with thousands of radioactive particles from the depths of space. Scientists have until recently been puzzled with the origin of these particles, but recent studies have found a likely source. With all the advances in technology since the discovery of these particles, we are finally close to determining where they come from, and subsequently how they are accelerated to such high energies.

The first conclusive observation of cosmic rays came in 1911 by a physicist named Victor Hess. “Hess showed that the Earth was constantly being bombarded by some kind of ionizing radiation of extraterrestrial origin, although he was unable to determine it’s exact nature” (Brunstein 36). These rays were originally believed to be some form of gamma radiation, but have since been revealed as highly charged nuclear particles. The information that has been gathered from cosmic rays and their composition has helped to make many discoveries, including the existence of previously undetected subatomic particles.

In the 1950’s the development of particle accelerators allowed us to charge certain particles to energies similar to those of standard cosmic rays, but nowhere near as powerful as the much rarer high energy rays. Standard cosmic rays have an average energy of 109 eV, or electron volts, where the highest energy rays have been measured up to 1019 eV. Man made particle accelerators can charge a particle to anywhere from 106 to 1011 eV. “Physicists have struggled for decades to determine where such ultrahigh-energy cosmic rays come from, and how they are accelerated to energies 100 million times greater than particle accelerators have reached” (Cho 896). If mankind could discover how to produce that kind of energy, it would cause irrevocable change around the world.

But the first big step to explaining these particles has been taken by the Auger collaboration, a 300 member team of astrophysicists. The Auger team had an area of 3000 square kilometers in Argentina covered with over 1300 detectors and special telescopes. The detectors analyze the shower of particles caused when a ray smashes into our atmosphere, and the telescopes have a special lens that allows them to actually see the particles falling from the sky.

Using data collected between 2004 and 2006 the physicists at Auger have calculated that the highest energy rays generally come from within three degrees of an “active galactic nuclei” (AGN), defined by Wikipedia as “a compact region at the center of a galaxy which has a much higher than normal luminosity over some or all of the electromagnetic spectrum” (Par. 1). The high quantity of electromagnetic radiation is believed to be caused by matter falling into the super-massive black hole that is thought to reside at the center of the AGN. “The cosmic rays do not pair precisely to the AGNs; presumably, the galaxy’s magnetic field deflects them in transit” (Cho 896). Yet only AGNs within 250 million light years of earth can be a viable source. Any farther and the particles would begin to lose energy due to the microwave radiation still present from the big bang.

Alan Watson, spokesperson for the Auger collaboration, says that the results do not prove AGNs to be the source, as it could be anything with a similar distribution through the sky. Because galaxies have a tendency to clump together, Watson suggests it could also be another type of galaxy that resides near the AGNs. The correlation between the AGNs and the cosmic rays was definitely strong enough to warrant further investigation, so the Auger collaboration took the correlation parameters from their previous data and applied it to their findings from 2006 to August of 2007, and confirmed a definite correlation. Though the data still fails to prove the AGNs as the source, they are now the most likely candidates.

The Auger team is not the first to claim to have located the origins of these high energy rays. Two theorists from the Russian Academy of Sciences in Moscow, Peter Tinyakov and Igor Tkachev, using data