Novel Approach In Hunt For Cosmic Particle Accelerator


A composite image of the supernova remnant SN 1006. Credit: X-ray: NASA/CXC/Rutgers/G.Cassam-Chenaï, J.Hughes et al.; Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical: Middlebury College/F. Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS

A composite image of the supernova remnant SN 1006. Credit: X-ray: NASA/CXC/Rutgers/G.Cassam-Chenaï, J.Hughes et al.; Radio: NRAO/AUI/NSF/GBT/VLA/Dyer, Maddalena & Cornwell; Optical: Middlebury College/F. Winkler, NOAO/AURA/NSF/CTIO Schmidt & DSS

A team of astronomers led by Sladjana Nikolić from the Max Planck Institute for Astronomy has observed the supernova remnant SN 1006, probing in unprecedented detail the region where the gas ejected during the supernova meets the surrounding interstellar matter. Such remnants have long been thought to be the source of cosmic ray particles hitting Earth. The observations show, for the first time, the presence of “seed particles”, possible precursors of such cosmic rays. The novel approach used by the astronomers promises further insights as to how supernovae remnants act as cosmic particle accelerators. The results will be published on February 14, 2013 in the journal Science.

When Victor Hess first discovered cosmic ray particles hitting Earth almost exactly a hundred years ago, he had little notion about their origin. Since then, ever more sensitive observations of these particles have turned up a number of sources. Among them are supernova remnants – cosmic blast waves launched by stellar explosions; expanding gas shells flung into space when certain stars end their lives in a supernova.

Where such a blast wave meets the surrounding interstellar medium, there is an abrupt change in density and temperature: a shock front similar to the sonic boom produced by an aircraft going supersonic. This expanding, high-velocity shock front is a natural candidate for a cosmic particle accelerator. Now, for the first time, astronomers have found observational evidence of accelerated protons in these shock regions. While these are not the sought-for high-energy cosmic rays themselves, they could be the necessary “seed particles”, which the go on to interact with the shock to reach the extremely high energies required and fly off into space as cosmic ray particles.

Full Story: http://www.mpia.de/Public/menu_q2e.php?Aktuelles/PR/2013/PR130214/PR_130214_en.html
Also: http://www.eso.org/public/news/eso1308/

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