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Music

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Narrator: This is the supermassive black hole at the

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center of NGC 4151. The dark object

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in the middle is the black hole. Surrounding it is a flattened cloud of dust

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and gas, called an accretion disk. Recently,

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scientists using the XMM-Newton X-ray satellite showed that a mysterious

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source of X-ray flares actually lies high above the disk.

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About half an hour after each flare, the inner accretion disk lights up with an

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X-ray "echo." The delay is caused by the time it light from the flare to reach

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the disk. This is first clear measurement of the effect, and demonstrates

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that the flaring X-ray source lies well above the disk. With flares

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serving as "flash-bulbs," future X-ray telescope missions will be able to use

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their echoes to precisely map the environs of distant black holes.