Dead Star Flings Gamma Rays in Pulses

Oct. 16, 2008 -- Scientists were putting a new space telescope through its paces when they found something odd -- a pulsating star, or pulsar, beaming only in gamma rays.

The discovery, published in this week's issue of Science, is the first finding from NASA's Fermi Gamma Ray Space Telescope, which was launched in June. It solves a mystery uncovered by a predecessor telescope and offers an explanation to a host of similar unexplained phenomena.

The pulsar detected by Fermi is associated with a supernova remnant known as CTA 1, the remains of a massive star in the Milky Way galaxy that exploded about 10,000 years ago. It is located about 4,600 light-years away in the constellation Cepheus.

Typically, supernova remains include the dead star's collapsed core -- known as a neutron star because its protons and electrons have combined to form neutrons.

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Sometimes the neutron star is spinning, which causes jets of particles to stream out above their magnetic poles, producing powerful beams of light that appear as flashes as the star rotates. These are known as pulsars, and their beams have been found in radio wavelengths, X-ray and, now for the first time, in gamma rays as well.