Visual Binary

Science Daily: Astronomers detect orbital motion in pair of supermassive black holes - VLBA reveals first-ever black-hole 'visual binary'

summary - Images made with the continent-wide Very Long Baseline Array detect the orbital motion of two supermassive black holes as they circle each other at the center of a distant galaxy. The two black holes themselves may eventually merge in an event that would produce gravitational waves that ripple across the universe.