black hole
noun
1- Astronomy a region of space having a gravitational field so intense that no matter or radiation can escape【天文】黑洞。
1.1
- informal a place where money or lost items are thought of as going, never to be seen again〈非正式〉“黑洞”（指钱财或失物一去不复返的地方）。
Black holes are probably formed when a massive star exhausts its nuclear fuel and collapses under its own gravity. If the star is massive enough no known force can counteract the increasing gravity, and it will collapse to a point of infinite density. Before this stage is reached, within a certain radius (the event horizon) light itself becomes trapped and the object becomes invisible.