You know about black holes; spaces of intense gravitational pull that suck in everything around them without so much as a second thought. On the other hand, they’re stationary, right? There’s no danger of a black hole accidentally wandering into Earth’s orbit and sucking the planet into it. Actually, there is. Rogue black holes are black holes that move throughout the stars, spelling doom for whatever poor planets they come across. What’s worse, you can’t see them coming. They’re invisible; all that can be seen is their effects. And to add fuel to the fire, these aren’t rare; hundreds have been discovered already.