This Week in Astronomy: Dark Matter, Biggest Black Hole Merger and Hidden Galaxies

Scientists propose that "dark dwarfs"—brown dwarfs powered by dark matter—could reveal what dark matter is made of. Meanwhile, LIGO and its partners detected the most massive black hole merger ever seen, offering new insights into black hole formation. At the same time, new simulations suggest there may be many hidden, faint galaxies orbiting the Milky Way, helping to solve a mystery in our understanding of dark matter and galaxy formation.