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An artist's concept shows a pulsar -- the rapidly spinning corpse of an exploded star. The explosion crushed the star's core and caused it spin rapidly. As it spins, it beams radio waves and other forms into energy into space, creating "pulses" of energy. Pulsars were discovered in 1968. [NASA/Dana Berry]
Graduate student Jocelyn Bell was using a radio telescope to study the mysterious objects known as quasars when she discovered a new mystery object. She detected a signal -- a pulse of energy that repeated every 1.3 seconds. It came from the same spot in the sky, day after day. She ruled out interference from the ground or from orbiting satellites. Bell and her advisor, Anthony Hewish, thought that perhaps the signal came from an alien civilization. So they playfully designated the object LGM-1 -- LGM for “Little Green Men.”
By the time they published their findings 40 years ago yesterday, they’d ruled out that possibility. In part, that was because they’d found three similar objects in different parts of the sky.
But just because it was natural didn’t make their discovery any less mysterious. Other astronomers joined the hunt for these pulsing objects, and within months they’d found a bunch of them. Most thought that they were the collapsed remnants of stars, but no one could figure out how they were beaming pulses of energy into space.
The answer came from another astronomer, Thomas Gold. He surmised that “pulsars” were rapidly spinning neutron stars -- objects that had been predicted but never seen. As they rotated, they beamed out pulses of energy like a lighthouse -- beacons marking the death sites of stars. More about that tomorrow.