Astro Bob: This is an artist view of a black hole. Because no light escapes the hole, in this depiction we’re able to see its outline because the hole’s colossal gravity bends and distorts the light of the more distant stars around its circumference. If we could see its internal contours, a black hole would appear funnel-shaped. At the bottomost, narrow end of the funnel, matter is squeezed into a point of infinite density called a singularity. Credit: NASA/ESA/ G. Bacon STScI It’s hard to visualize a black hole because you can’t see one directly. A black hole’s gravity is so strong, not even light can escape. Without light to let us know it’s there, we see only darkness, hence the name. Luckily, black holes can be “seen” by calculating how fast stars and gas clouds spin around them. From these observations, we learn how massive the object must be to do the spinning. Then when we look for that object and if we see nothing there, we’re left with the only reasonable alternative: a black hole. In this black hole illustration, infalling matter forms a brilliant disk of heated gas around the black hole before crossing the event horizon (gray bubble) ...