Ten thousand years ago, when saber-toothed cats and woolly mammoths still roamed the earth, a star exploded in the constellation Cepheus, 4,600 light-years away. Whoever saw it then must have marveled at it's brightness, which must have been visible also during the say.
Today, that cataclysmic explosion has left a circular remnant that's about three full moons in diameter. Scientists have known for a long time that there was something strange about it. They had detected some form of radiation in the vicinity. "Nobody knew where it was coming from," said Alice Harding of the Goddard Space Flight Center in Greenbelt, Md.
Only lately, when astronomers were testing NASA's Fermi Gamma Ray Space Telescope, that they discovered it to be a pulsar - a neutron star releasing pulses of radiation. What's new about this pulsar is that it was streaming gamma radiation, which was unheard of until then. Pulsars, like the Vela Pulsar (left), have been known to emit radiation in the radio and x-ray wavelengths. Now that astronomers know gamma pulsars exist, they expect to find more.
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