By Ron Cowen
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