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Gamma-Ray Bursts II

April 19, 2016

Last September, the universe jiggled. An observatory detected gravitational waves from the merger of two black holes more than a billion light-years away. It was the first direct detection of gravitational waves, which were predicted by Albert Einstein.

Just four-tenths of a second after the waves rippled past Earth, a space telescope detected a flash from the same region of the sky. It lasted for less than a second, but it emitted more energy than the Sun will produce in its entire lifetime.

That flash was known as a gamma-ray burst. Space telescopes see about one such outburst per day. They’re the most powerful events in the universe. And they fall into two classes. One lasts for a few seconds to a few hours — probably triggered by the death of a massive star; more about that tomorrow.

The other class lasts no more than two seconds, and that’s the class that was seen last year. Theory says these bursts occur in the merger of two stellar “corpses” — a neutron star and a black hole. The black hole takes a bite out of the neutron star, producing a brief but brilliant outburst.

But the gravitational waves from last year’s event show that it was the merger of two black holes. That could mean that the waves and the gamma rays came from different events that just happened to show up at the same time and place. But it also could mean that the merger disrupted a disk of material around the black holes — producing a brief but brilliant outburst.


Script by Damond Benningfield

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