Instead, it seems that the black holes are still growing at the present time. Supermassive black holes, likely created from collapsed gas clouds, contain the mass of millions to billions of stars confined to a region no larger than our Solar System. Astronomers now believe that most galaxies, including our own, harbor a supermassive black hole at their core. This matter, heated to millions of degrees under the crushing force of gravity, shines particularly bright in X-ray light as well as in other wavebands. Barger looked at these same sources with ground-based optical, submillimeter and radio telescopes.
Optical measurements reveal the times at which the black hole activity occurred.
Submillimeter and radio measurements provide crucial information on the amount of energy emitted in the formation of the supermassive black holes. With such follow-up, the team was able to map the energy production by supermassive black holes throughout the history of the Universe and determine the time history of the supermassive black hole formation process. The discovery that 10 percent of the black holes are active at any time implies that black hole growth is a slow, ongoing process with the galaxies spending more than a billion years in creating the black holes at their centers. Moreover, the time intervals found for the black hole growth are much longer than would be expected if the black holes were formed in violent galaxy mergers, as has often been speculated. The Keck 10-meter telescope and the James Clerk Maxwell telescope, both located on Mauna Kea in Hawaii, were used to obtain the optical and submillimeter observations, respectively.