Markarian 231, host galaxy of double black hole

This Hubble Space Telescope image reveals a bright starlike glow in the center of the interacting galaxy Markarian 231, the nearest quasar to Earth. Located 600 million light-years away, we are seeing the galaxy as it looked before multicelled life first appeared on Earth. Quasars are powered by a central black hole that heats the gas around it to unleash tremendous amounts of energy. Hubble spectroscopic observations infer the presence of two supermassive black holes whirling around each other. Because such a dynamic-duo pair are found in the nearest quasar, it would imply that many quasars host binary-black-hole systems. It would be a natural result of a galaxy merger.