(Credit: NRAO, AUI, NSF) We're probably going to get our very first actual picture of a black hole next week. Researchers with the Event Horizon Telescope (EHT) have scheduled a press conference for the morning of April 10, and they're expected to unveil an image of a supermassive black hole. It will be the first time humanity has actually seen one of the massive objects with our own eyes, and scientists are understandably excited about what the image will tell them.
Cosmic Elephants
But, images of black holes have been circulating for years, right? Magazines, including this one, routinely run pictures of black holes alongside stories — you probably already have a mental image of what I'm talking about. Black sphere, colorful spiral of gas ... don't we already know what a black hole looks like? Well, kind of. All of those pictures are artistic representations based, sometimes loosely, on theories about what physics tells us a black hole should look like. So, we have a pretty good idea of what a black hole might look like. The reality, however, is that we don't actually have any confirmation. As EHT member Katie Bouman puts it in a TEDx talk, there could be an elephant at the center of our galaxy for all we know. We'll likely know the truth soon, though it won't necessarily look anything like what we may have come to expect. That's for two main reasons. First, black holes are so far away that the picture will probably be much blurrier than most artistic representations show. Also, Albert Einstein's theory of general relativity tells us that spacetime bends in weird ways near a black hole — a fact not usually accounted for by artists. There's another reason that drawings of black holes take some degree of liberty, one that's staggeringly obvious: You can't see a black hole. By definition, a black hole is a region of space where no light escapes. No light means no picture. This means that quiet black holes, those that aren't sucking up gas or other matter, are effectively invisible. And for those that are snacking on matter, called active black holes, it's no straightforward task either. Thick dust clusters around many active black holes, shrouding their forms. Some betray their presence with powerful jetes of matter thousands of light-years long, though their hearts often remain hidden. The most blindingly bright of these are called quasars, and they are indeed hard to miss. But quasars are by far the minority.
