What does a black hole look like? Well, it's sort of like the wind: When you see the leaves blowing off a tree or your friend's hair pushed back by the breeze, it's not the wind itself you're seeing, but rather, its effect on the surroundings. Black holes are similar: Their gravity is so intense that not even light escapes them, so there's nothing for us to really see. But these cosmic monsters can still light up the night.
We've seen illustrations of black holes — or rather, the gasses surrounding black holes as they heat up on their march towards oblivion — but what would it look like to see an actual black hole in the night sky, given that you could see the intense x-rays these gases gave off? The folks at NASA’s Chandra X-Ray Observatory just posted a photo on Twitter showing exactly that, and it's marvelous:
— Chandra Observatory (@chandraxray) January 6, 2017
Like they said, above is the highest concentration of black holes we've ever seen, although this isn't anything we could see with our human eyes. The Chandra Observatory uses X-rays, which are given off by the heated gasses being sucked into black holes, instead of visible light.