英语听力：黑洞吞噬—25

Galaxies could in a way, be much bigger than they currently are. Something is stopping them growing larger and that something is the black hole at the center. Now this is bizarre because the ration of the size of the black hole to the size of the galaxy is the same as the ratio between a grape, something this big, and the size of the earth. Now you might think that it’s impossible for something that small to control something that large. But that’s what appears to be happening.

As the black hole begins to devour matter, so it starts to pull out energy. Like a cosmic brew, that energy sweeps matter back out from the center of the galaxy, preventing it from clamping together to form new stars.

The conclusion of this is the total number of stars forming a galaxy appears to be stopped,truncated by the power of the black hole at the center.

The discovery of that relationship has turned every preconception about the nature of black holes on its head. Instead of being strange cosmic aberrations, black holes have moved to the very center of the story of galaxies and stars, a story that must include our own solar system. And that must mean that in some way, our own black hole must have played a part in what is perhaps the greatest mystery of all.