Astronomers have found the nearest known black hole candidate to Earth, a quiet beast nearly ten times as massive than the Sun just 1,570 light-years from us * . It was found through the antics of its Sun-like stellar companion, but how it came to be is a head-scratcher [ link to paper ]. There are likely a hundred million black holes in our Milky Way galaxy alone, but finding them is difficult. The easiest way is if they are in a binary system with a companion star, and they’re close enough together that material is stripped from the star and falls into the black hole. As it piles up outside That Last Big Step the material heats up and emits a lot of high-energy radiation , basically announcing the black hole’s existence. But if the black hole is alone, or is in a binary with the star orbiting farther out, it’s quiescent , making it hard to detect. The thing about black holes is they’re black , so they can only be detected via their immense gravity .…