Q&A: Black Holes

Q:
If X-rays are produced by a high-speed collision between an electron and a proton and X-rays are observed to emanate from the cores of galaxies (among other places) why can't we speculate upon a proton star in the center? Why does theory predict that a black hole is accelerating matter that emits X-rays instead of a Protonic star whose electromagnetic strength is attracting electrons that in turn emit the X-rays?

A:
There are two problems with a pure proton star model. First, the repulsive force between the protons would blow it apart, unless gravity was strong enough to prevent it. But if gravity was that strong, the star would collapse to form a black hole. Second, even if a milder version of such a star could exist, with an electrified outer atmosphere, electrons would very quickly accelerate to the star in the manner you describe, produce a bright flash of X-rays and gamma-rays, and then it would all be over because the electric field would have been shorted out, or neutralized. Such as model involving electric fields created temporarily around black holes, has been suggested as a model for gamma ray bursts. See:
http://chandra.harvard.edu/press/01_releases/press_071201.html