Most astronomers believe that the large concentration of mass at the galaxy's center is a black hole whose gravity is causing the gas to whirl.
大多数天文学家认为，星系中心的大量物质是一个黑洞，它的引力导致气体旋转。
2
A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior.
一个黑洞是物质浓缩到足够大的以致引力除了通过量子隧道行为之外阻止任何东西从它那里逃逸。
3
Most astrophysicists accept that this is the case, since according to general relativity, any concentration of matter of sufficient density must necessarily collapse into a black hole.