Certain black holes shine more brightly than the stars around them. In fact, black holes can be some of the brightest objects in their part of the galaxy. This seems counterintuitive, given that nothing, not even light, can escape a black hole. But what's shining is not the "hole" itself, which is invisible to the human eye, but the matter spiraling around it in what's called the accretion disk. This disk is made of the gas and dust that the black hole is attracting with its gravitational pull. Once ensnared, this material tries to orbit the hole, and parts of it that are closer to the event horizon are subject to higher gravitational forces. The resulting friction causes the material to heat up, sometimes to millions of degrees Kelvin, and to glow with an extreme brightness that is recognizable to astronomers.
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Key Facts In This Video
At the heart of a black hole is the singularity, a region of highly compressed matter. 01:44
Light inside the event horizon of a black hole cannot escape. 02:47
Excess gas, dust, and material gather around black holes in disks that heat up and glow. 03:34