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Astronomers measure nearby Universe’s ‘cosmic fog’

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Cosmic history and opacity to gamma-rays at different periods, as measured by HESS and Fermi-LAT. The vertical axis of the graph shows opacity normalized to a reference model (Franceschini et al., 2008), while the horizontal axis shows the distances in light years of the blazars used for the measurements. The blue point on the left shows the range within which the Fermi measurements are statistically significant, and the red point on the right shows the measurements carried out by HESS in the nearby Universe. Credit: HESS Collaboration

Cosmic history and opacity to gamma-rays at different periods, as measured by HESS and Fermi-LAT. The vertical axis of the graph shows opacity normalized to a reference model (Franceschini et al., 2008), while the horizontal axis shows the distances in light years of the blazars used for the measurements. The blue point on the left shows the range within which the Fermi measurements are statistically significant, and the red point on the right shows the measurements carried out by HESS in the nearby Universe. Credit: HESS Collaboration

Researchers from the Laboratoire Leprince-Ringuet (CNRS/École Polytechnique) have carried out the first measurement of the intensity of the diffuse extragalactic background light in the nearby Universe, a fog of photons that has filled the Universe ever since its formation. Using some of the brightest gamma-ray sources in the southern hemisphere, the study was carried out using measurements performed by the HESS telescope array, located in Namibia and involving CNRS and CEA. The study is complementary to that recently carried out by the Fermi-LAT space observatory. These findings provide new insight into the size of the Universe observable in gamma rays and shed light on the formation of stars and the evolution of galaxies. They feature on the cover of the 16 January 2013 issue of the journal Astronomy & Astrophysics online…..
Read more at: http://phys.org

Written by physicsgg

January 20, 2013 at 7:29 pm

Posted in ASTROPHYSICS, COSMOLOGY

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