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In 1967 something remarkable was discovered in the sky: a star that appeared to be pulsing on and off with a period of about a second. Shortly, other such "pulsars" were discovered and the fastest now known pulse on and off at nearly a thousand times a second. The only plausible explanation for such pulsars is that they are rapidly spinning neutron stars, with a mechanism to beam radiation in a kind of lighthouse effect. Some of these pulsars contain the strongest magnetic fields known in our galaxy.

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