Take a dense, collapsed star, set a helium-rich star in orbit around it, and you've got the
ingredients for a series of explosions, each lasting about 10 seconds and releasing as much
energy as the sun does in an entire year.
Such eruptions can happen several times a day on the surface of a neutron star—the superdense
cinder left behind when a massive star jettisons its outer layers and collapses. Now,
astronomers have glimpsed a much rarer, longer-lived neutron-star explosion that unleashed
100 times as much energy.
In the more common explosions, a neutron star, as heavy as the sun but only 20 kilometers
wide, snatches gas from a nearby companion rich in helium. As the stolen helium piles up on
the neutron star's surface, helium nuclei fuse explosively, briefly hurling a torrent of X rays
Last year, astronomers using the Rossi X ray Timing Explorer satellite examined a neutron
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