NASA's Fermi Closes on Source of Cosmic Rays
02.16.10
Fermi mapped GeV-gamma-ray emission regions (magenta) in the W44 supernova remnant. The features clearly align with filaments detectable in other wavelengths. This composite merges X-rays (blue) from the Germany-led ROSAT mission, infrared (red) from NASA's Spitzer Space Telescope, and radio (orange) from the Very Large Array near Socorro, N.M. Credit: NASA/DOE/Fermi LAT Collaboration, ROSAT, JPL-Caltech, and NRAO/AU
Cosmic rays consist mainly of protons that move through space at nearly the speed of light. In their journey across the galaxy, the particles are deflected by magnetic fields. This scrambles their paths and masks their origins.
"Understanding the sources of cosmic rays is one of Fermi's key goals," said Stefan Funk, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly located at SLAC National Accelerator Laboratory and Stanford University, Calif.
When cosmic rays collide with interstellar gas, they produce gamma rays.
"Fermi now allows us to compare emission from remnants of different ages and in different environments," Funk added. He presented the findings Monday at the American Physical Society meeting in Washington, D.C.
http://www.nasa.gov/mission_pages/GLAST/news/cosmic-rays-source.html