View Count: 165 |  Publish Date: March 16, 2013
Cosmic 'fog' may hold secrets of universe's formation
A diffuse “fog” of photons fills much of our universe, and some first-ever measurements of it, conducted by researchers from the French research institutions National Center for Scientific Research (CNRS) and the Atomic Energies Commission (CEA), are yielding new insights into how stars form and galaxies evolve. The researchers studied gamma ray sources via HESS, a French-German telescope observatory in Namibia.
This photon fog—its formal name is “diffuse extragalactic background light”—emits from all of the stars, galaxies, and other objects that compose the universe, and it has been present since the universe’s beginning. It is impossible to directly observe it, since the luminosity of our own galaxy drowns it out. Astrophysicists instead study it by observing gamma rays, an energy that galaxies and stars also release and which holds 500 billion times more energy than visible light. The diffuse extragalactic background light weakens the gamma rays as they travel through it, and human researchers can measure the concentrations and intensity of the background light by studying the weakness of the rays—the weaker the gamma rays appear to be, the stronger the background light is.
Once the gamma rays reach Earth, the planet’s atmosphere absorbs them. The interaction creates a shower of subatomic particles, which produces flashes of light. HESS’s telescopes are able to capture these flashes.
In this study, the CNRS-CEA team focused on background light coming from “blazars,” a category of galaxies that are several billion light-years distant from Earth. They proceeded to evaluate the effect of background light on gamma rays that come from the cosmic bodies that lie within three billion light-years of Earth, and then they conducted the same measurements for cosmic bodies that are five billion to ten billion light-years away. The final analyses produced, for the first time, fairly precise estimates of the intensity of the full range of starlight within the universe, from the range of near infrared all the way through to the ultraviolet, including the visible wavelengths in between.
This study, which featured in the January 16, 2013, issue of the online journal Astronomy & Astrophysics, essentially presents a record of the luminous universe and information about the earliest stars. The researchers hope to incorporate the data into models of how stars have been forming since the universe’s earliest beginning stages, and it may shed light on the birth of the universe’s very first stars and star systems. The study’s findings may also facilitate study of the mechanisms of intergalactic magnetic fields and of other lesser-known physical phenomena.

Time: 16:28  |  News Code: 208902  |  Site: sciencerecorder
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