If nothing can escape a black hole, why do they still emit x-rays?

It is true that once matter or energy passes within the so-called Event Horizon of a black hole, that it can never turn around and get backout. However, in the real world, a lot can happen to matter as it approachesthe Event Horizon. Commonly, matter falls into what is called anaccretion disk which orbits the black hole. Material orbits the black holewithin this disk, but if it happens to be gas and dust, this matter experiences friction and the disk heats up as some of the orbitalenergy of the gas is converted into heat. The closer the disk material isto the black hole, the more rapidly it orbits so that the greater is the heating effect. Just before it reaches the Event Horizon, this disk matter can be heated by friction to thousands of degrees which is enough to produceX-rays. Even higher temperatures approaching a million degrees can occurwhich can produce gamma rays.

This disk radiation, being outside the black hole, is what we detect as welook at black holes.

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