"An artist's illustration shows a binary black hole found in the quasar at the center of the Markarian 231 galaxy. Astronomers using NASA's Hubble Space Telescope  <a href=""http://www.cnn.com/2015/08/31/us/double-black-hole-nasa-hubble-feat/"" target=""_blank"">discovered the galaxy being powered by two black holes</a> ""furiously whirling about each other,"" the space agency said in a news release."