Gamma-Ray Bursts

StarDate: January 26, 2009

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At the height of the Cold War, American satellites scanned Earth and the space around it for exploding nuclear bombs. They didn't find any. But they did find some explosions that made H-bombs seem like bursting soap bubbles by comparison. These gamma-ray bursts are the most powerful events in the universe.

Gamma rays are the most powerful form of energy. But Earth's atmosphere blocks them, so no one had seen a gamma-ray burst until detectors were placed in orbit.

Early instruments picked up flashes of gamma rays that lasted from a fraction of a second to a few minutes. But by the time astronomers could turn other telescopes toward the outbursts, there was nothing to see -- there was no glowing ember in the form of visible light or any other form of energy.

With only the initial bursts of gamma rays to go on, astronomers couldn't figure out where the bursts were coming from -- inside our own Milky Way galaxy, or far beyond it.

But in the 1990s, new space telescopes found that the bursts are found across the entire sky, which means they can't be confined to the Milky Way.

And in 1997, astronomers finally managed to turn their telescopes toward a burster quickly enough to see the fading glow of visible light. Hubble Space Telescope looked at that spot in the sky and found a distant galaxy. The discovery confirmed that gamma-ray bursts are far, far away -- so they must be extremely powerful. More about that tomorrow.

Script by Damond Benningfield, Copyright 2008

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