Auger Observatory closes in on long standing mystery,
links highest-energy cosmic rays with violent black holes
Scientists of the Pierre Auger Collaboration announced today (8 Nov. 2007) that active galactic nuclei are
the most likely candidate for the source of the highest-energy cosmic rays that hit Earth. Using the Pierre
Auger Observatory in Argentina, the largest cosmic-ray observatory in the world, a team of scientists from 17
countries found that the sources of the highest-energy particles are not distributed uniformly across the sky.
Instead, the Auger results link the origins of these mysterious particles to the locations of nearby galaxies
that have active nuclei in their centers. The results appear in the Nov. 9 issue of the
Active Galactic Nuclei (AGN) are thought to be powered by supermassive black holes that are devouring large
amounts of matter. They have long been considered sites where high-energy particle production might take place.
They swallow gas, dust and other matter from their host galaxies and spew out particles and energy. While most
galaxies have black holes at their center, only a fraction of all galaxies have an AGN. The exact mechanism of
how AGNs can accelerate particles to energies 100 million times higher than the most powerful particle
accelerator on Earth is still a mystery.
The celestial sphere in galactic coordinates (Aitoff projection)
showing the arrival directions of
the 27 highest energy cosmic rays detected by Auger. The energies are greater than 57 x 1018 eV
(57 EeV). These are shown as circles of radius 3.1°. The
positions of 472 AGN within 75 megaparsecs are shown as red *'s. The blue region defines the field of view
of Auger; deeper blue indicates larger exposure.
The solid curve
marks the boundary of the field of view, where the zenith angle equals 60°.
The closest AGN, Centaurus A, is marked as a white *. Two of the 27 cosmic rays
have arrival directions within 3° of this galaxy.
The supergalactic plane is indicated by the dashed curve. This plane delineates a region where large numbers of
nearby galaxies, including AGNs, are concentrated.
Click on the image for a better view.
The links below point to press information provided by the collaborating countries of the Pierre Auger