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Gamma-Ray Bursts III

April 20, 2016

The birth of a black hole can be a violent event.

The nuclear reactions in the core of a massive star come to an end, so the core collapses to form the black hole. Gas in the star’s outer layers falls toward the black hole, where some of it is heated to billions of degrees. Some of that gas forms a swirling disk around the black hole, but some punches through the star’s poles, creating a brilliant flash of energy.

If the poles happen to aim toward Earth, then space telescopes can see the flash as a gamma-ray burst — the most powerful type of outburst in the universe. In a few seconds or minutes, it can radiate more energy than the Sun will produce in its entire 10-billion-year lifetime. And the gamma-ray burst is followed by a supernova, as the star’s outer layers blast out into space.

That’s the leading explanation for gamma-ray bursts that last for two seconds or longer. Some of them appear to be powered by stars that are about as big as the Sun, but many times more massive. These outbursts last up to a few minutes — the time it takes their stars’ outer layers to collapse, then explode into space.

Other gamma-ray bursts can last for hours. These also appear to be powered by heavy stars, but the stars are also many times bigger than the Sun. It takes a long time for their outer layers to collapse and explode, so the jets last a lot longer — and so does the gamma-ray burst — the possible birth of a black hole.

More tomorrow.


Script by Damond Benningfield

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