Comment Common Misconceptions about a Black Hole (Score 2, Interesting) 143
A black hole is not a literal physical singularity. There are "bigger" ones and "smaller" ones. It is instead a mathematical singularity: it can be treated as a point object in the sense that if you lay out a gravitational grid across the universe, each black hole is a point, a hole on that grid where nothing comes out.
So why do black holes emit X-rays and Hawking radiation or why do they emit stuff at all?
The black holes don't emit anything per se. However, as particles close to the event horizon are accelerated more and more by the gravitational pull of a black hole, THEY can emit radiation. An illustrative model is a star/black hole binary system in which gases from the star are being pulled in to the black hole, thus emitting X-rays as they are accelerated.
Hawking radiation is also not really emitted from the black hole itself. Theory goes quantum fluctuations occur so close to the event horizon that one particle gets sucked in while the other escapes: imagine a positron-electron pair appearing right on the cusp of an event horizon. Let's say the positron disappears into the black hole while the electron escapes out into the universe. From our perspective, the electron will have been "emitted" from the black hole. The energy required for this is also taken from the black hole as the positron (think of it as negative energy) will go into the black hole and take that much energy away from it.
So why do black holes emit X-rays and Hawking radiation or why do they emit stuff at all?
The black holes don't emit anything per se. However, as particles close to the event horizon are accelerated more and more by the gravitational pull of a black hole, THEY can emit radiation. An illustrative model is a star/black hole binary system in which gases from the star are being pulled in to the black hole, thus emitting X-rays as they are accelerated.
Hawking radiation is also not really emitted from the black hole itself. Theory goes quantum fluctuations occur so close to the event horizon that one particle gets sucked in while the other escapes: imagine a positron-electron pair appearing right on the cusp of an event horizon. Let's say the positron disappears into the black hole while the electron escapes out into the universe. From our perspective, the electron will have been "emitted" from the black hole. The energy required for this is also taken from the black hole as the positron (think of it as negative energy) will go into the black hole and take that much energy away from it.
