An artist's illustration shows a supermassive black hole with millions to billions times the mass of our sun at the center, surrounded by matter flowing onto the black hole in what is termed an accretion disk in this NASA illustration released on February 27, 2013. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. This disk forms as the dust and gas in the galaxy falls onto the hole, attracted by its gravity. (Photo by Reuters/NASA/JPL-Caltech)
