Team garners cover story in prestigious journal Science

Jim Matthews

Jim Matthews, professor of physics at Southern University, Baton Rouge and professor of physics and astronomy at LSU, partnered with scientists from 17 countries to help the Auger Observatory in Argentina take a historic step toward understanding high energy cosmic rays and their connection to violent black holes, linking the origins of these mysterious particles to the locations of nearby galaxies that have active nuclei in their centers. The effort was the subject of the November 9 cover story in the journal Science

"Cosmic rays have been known about for more that one hundred years, but we've never understood where they all come from," said Matthews. "This is a start. It helps us understand the universe we live in a little better and how matter itself behaves at high energies."

Cosmic rays are protons and atomic nuclei that travel across the universe at close to the speed of light. When these particles smash into the upper atmosphere of Earth, they create a cascade of secondary particles called an air shower that can spread across 40 or more square kilometers - approximately 15 square miles - as they reach Earth's surface.

While the observatory has recorded almost a million cosmic ray showers, only the rare, highest-energy cosmic rays can be linked to their sources with any true precision. At these high energies, the directional uncertainty of the ray's area of origination shrinks to a matter of degrees, allowing scientists to determine the location of the particle's cosmic source.

The Auger team found that most of the rays seem to match with the locations of Active Galactic Nuclei, or AGN, in some nearby galaxies, such as Centaurus A. AGN are thought to be powered by super massive black holes devouring large amounts of matter. Swallowing gas, dust and other matter from their host galaxies and spewing out particles and energy, AGN have long been considered potential high-energy particle production sites.

While most galaxies have black holes at their center, only a fraction have an AGN. The exact mechanism of how AGN can accelerate particles to energies 100 million times higher than the most powerful particle accelerator on Earth is still a mystery.