What is a Black Hole?
A black hole is a region of space in which gravity is so extreme that it prevents anything from escaping. Around the black hole there is an event horizon that marks the point of no return. The hole is black in appearance because it absorbs all of the light that hits the horizon and reflects none of it. Black holes are formed from supernova explosions. These happen when giant stars die and have a gravitational collapse. This causes all of their mass and gravity to be put into a small area. Only the largest of star giants turn into black holes. Some black holes are formed from stellar collisions.
Are We Sure They Exist?
Yes, we know black holes exit because we have witnessed their effects on nearby areas. Although there was no word for it the idea of an object in space so massive and dense that even light could not escape it, has been around for centuries. Einstein’s theory of relativity predicted that black holes existed. We cannot directly observe black holes using telescopes but we can however determine that they exist by observing their effect on the nearby matter. We cannot see black holes because black holes don’t let light escape. This makes them nearly invisible, making it more difficult to find where black holes are located.