Paris, 15 january 2013

Nearby Universe's "Cosmic fog" measured

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 HESS1 telescope array, located in Namibia and involving CNRS and CEA. The study is complementary to that recently carried out by the Fermi-LAT2 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.

To download the press release CP-Nearby Universe's "Cosmic fog" measured


1 H.E.S.S.: 'High Energy Stereoscopic System'. The international HESS collaboration currently brings together 180 researchers from 28 laboratories in 12 different countries, mainly in Germany and France.
2 The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars. Ackermann et al., Science, published online on 1 November 2012 and in print 30 November 2012 (Vol. 338 no. 6111 pp. 1190-1192). 10.1126/science.1227160.


Measurement of the extragalactic background light imprint on the spectra of the brightest blazars observed with H.E.S.S.. Collaboration HESS. Astronomy & Astrophysics, on line 16 January 2013.

Contact information:

Researcher l Jonathan Biteau | T +33 (0)1 69 33 55 50 |
Berrie Giebels l T +33 (0)1 69 33 55 53 l
David Sanchez l
CNRS Press Office l Priscilla Dacher l T +33 (0)1 44 96 46 06 l


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