Scientists closing in on cosmic ray source 2007-11-09 05:37:41   Print

    WASHINGTON, Nov. 8 (Xinhua) -- An international research team announced Thursday 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 was published in the Nov. 9 issue of the journal Science.

    Active Galactic Nuclei (AGN) are thought to be powered by super-massive 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.

    After the detection of about 80 high-energy cosmic ray events, the research team reports that the most energetic cosmic rays they detected generally hail from areas of the sky that are populated by nearby Active Galactic Nuclei.

    According to the researchers, the cosmic rays may have been accelerated by the magnetic fields around the black holes, which would help explain their extreme energies.

Editor: Yan Liang
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