December 13, 2011

How to Make a Gamma Ray

The gamma-ray emission from Tycho’s supernova remnant can be explained by pion production. A proton traveling close to the speed of light strikes a slower-moving proton. Their interaction creates an unstable particle — a pion — with only 14 percent of the proton’s mass. In 10 millionths of a billionth of a second, the pion decays into a pair of gamma rays.  Credit: NASA’s Goddard Space Flight Center

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