Black holes hide behind event horizons, the distance within which not even light can escape their gravitational pull. They arise in the universe as the final death state of massive stars. Black holes millions of times the mass of our Sun also live in the centers of galaxies—there is one in the center of our own Milky Way. These dense, massive objects warp spacetime around them, trapping smaller companions into spectacular orbits. Black hole orbits are far more elaborate than the simple planetary orbits we see in our solar system.