Credit: Koyama, K., et al., Nature, 378, 255, 1995

Cosmic Ray Gun

Cosmic rays are mysterious streams of extremely fast moving subatomic particles (mainly protons and electrons) produced in space. Astronomers don't know precisely where all these particles come from. The sun is a known source of cosmic rays which are produced by high energy explosions (solar flares) in the sun's atmosphere, but the amount of cosmic rays emitted by the sun is too low to account for all the cosmic rays which strike earth. Astronomers for a long time have suspected that supernova explosions might be an important source of cosmic rays in the Galaxy. In a supernova, an enormous amount of material is exploded from a dying star; as this material encounters the surrounding gas in the galaxy, it produces a strong shock which might accelerate protons and electrons into cosmic rays. Observations by the ASCA satellite for the first time provided direct evidence that supernova actually do produce cosmic rays. The image on the above left shows an ASCA observation of the supernova remnant SN 1006. Measurements of the X-ray emission in the supernova remnant showed startling variations in the types of X-rays produced in the different parts of the remnant. The inset graph of the X-ray energy spectrum in the lower right tells astronomers that inside the remnant, X-rays are produced by hot gas. However, the graph of the X-ray spectrum of the bright edge of the remnant tells astronomers that the X-ray emission in the bright rim is produced by fast moving electrons spiralling around magnetic field lines. These electrons must have been accelerated by the blast wave from the supernova, showing that supernova explosions can indeed be a source of cosmic rays.

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Page Author: Dr. Michael F. Corcoran
Last modified November 9, 2000