Gamma-Ray Sky

StarDate: October 28, 2009

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The universe is filled with violence. Giant stars blast themselves to cosmic dust. Hot gas spirals into supermassive black holes at almost the speed of light. And particles of matter ram together like runaway trains.

These powerful events announce themselves to the universe with the most powerful form of energy, known as gamma rays. They contain millions of times as much energy as visible light, but they're invisible to human eyes. And even if we could see them, it wouldn't matter, because Earth's atmosphere prevents them from reaching the surface.

The only way to see gamma rays directly is to loft telescopes above the atmosphere with balloons or rockets. But we can see them indirectly with special detectors on the ground.

Gamma rays tell us about some of the most fascinating objects in the universe. That includes the objects known as gamma-ray bursts -- the most powerful outbursts in the entire universe. They may be created when a giant star blasts itself to bits -- perhaps giving birth to a black hole in the process. Such an outburst produces more energy in a few seconds than the Sun will produce in its entire lifetime.

Gamma rays also come from the disks of gas around black holes. The gas is accelerated to near lightspeed by the black hole's gravity, so it emits enormous amounts of energy.

And it's even possible that gamma rays could come from the mysterious stuff known as dark matter -- and we'll talk about that tomorrow.

Script by Damond Benningfield, Copyright 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

The one constant in the Universe: StarDate magazine

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