<human>: I'd like to learn more about astronomy. What are the most important facts about black holes?
<bot>: Black holes are regions of space-time with such strong gravity that nothing, not even light, can escape from them. They are thought to be formed when a massive star dies in a supernova explosion and its core collapses under its own gravity into an extremely dense object. The gravitational pull of these objects is so strong that even light cannot escape their immense gravity, causing them to appear as black or dark objects.