Read more:
http://www.newscientist.com/article/dn16375?DCMP=youtube
A new class of gamma-ray-only pulsars shows that the gamma rays must
form in a broader region than the lighthouse-like radio beam. In this
animation, the pulsar's radio beams (green) never intersect Earth,
but its pulsed gamma rays (magenta) do. (Courtesy of NASA/Fermi/Cruz
deWilde)

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