Tag Archives: SN remnant

Fermi observations proves Supernova Remnants produce Cosmic Rays

This multiwavelength composite shows the supernova remnant IC 443, also known as the Jellyfish Nebula. Fermi GeV gamma-ray emission is shown in magenta, optical wavelengths as yellow, and infrared data from NASA's Wide-field Infrared Survey Explorer (WISE) mission is shown as blue (3.4 microns), cyan (4.6 microns), green (12 microns) and red (22 microns). Cyan loops indicate where the remnant is interacting with a dense cloud of interstellar gas. Credit: NASA/DOE/Fermi LAT Collaboration, NOAO/AURA/NSF, JPL-Caltech/UCLA
Particles with TeV energies, like those produced at the LHC, seem exotic. But once outside the protection of our atmosphere, these “cosmic rays” (CR) become exceedingly common. The Fermi Telescope, for example, encounters a hundred thousand CR for every gamma ray it detects. These particles have an impressive scope of local effects, from damaging electronics and inhibiting manned space travel to possibly triggering lightning strikes. And although we have been aware of their existence since the early 1900ʼs, their exact origins remained unclear. Now a study by
the Fermi Collaboration claims to have solved the mystery.

The list of mechanisms capable of accelerating so many particles to high
energies was already a short one. Strong electromagnetic fields, like those surrounding pulsars, could do the job. So could the process for which the gamma-ray telescope got its name – Fermi acceleration. Less intuitive, it amounts to trapping particles in a region where they are repeatedly reflected by inhomogeneous magnetic fields. Each reflection supplies them with more energy, and the series of small enhancements adds up. One place there such conditions exist is at the boundary between slow and fast moving groups of particles, sometimes known as a “shock.” Supernova remnants (SNR), the
aftermath of massive astrophysical explosions, are expected to shock where the expanding sphere of stellar material encounters the surrounding gas.
Continue reading Fermi observations proves Supernova Remnants produce Cosmic Rays