Researchers at the University of Illinois at Urbana-Champaign and at the National Center for Supercomputing Applications have claimed that the luminosity of quasars is linked to the Black Hole mass. Astronomers at these two institutions are of the view that quasars are young galaxies powered by super-massive black holes at their centers, and they add that these black holes can be millions or billions of times more massive than our sun. According to Brian Wilhite, one of the astronomers participating in the study, quasars possess enormous sources of energy, which makes them "among the brightest objects in the universe, some giving off thousands of times more light than our own Milky Way galaxy from a region slightly larger than our solar system." Wilhite further goes on to say that most astronomers agree that quasars are incredibly variable, with some quasars quadrupling in brightness in the span of just a few hours. Recently, Wilhite and other researchers found that this variability is related to both the mass of the black hole at the center of the quasar, and to the efficiency of the quasar at converting gravitational potential energy into light energy. Using data obtained by the Sloan Digital Sky Survey, the researchers monitored the brightness and estimated the central black hole mass of more than 2,500 quasars, observed over a period of four years. They found that, for a given brightness, quasars with large black hole masses are more variable than those with low black hole masses. "Quasars with more massive black holes have more gravitational energy that can potentially be extracted, which we would see in the optical as light," said Wilhite, who presented the team's findings at the American Astronomical Society meeting in Seattle on Monday. The researchers' findings mark the first time that changes in light output of quasars have been related to their efficiency, and could prove useful in helping astronomers decipher the underlying physics that causes quasars to vary so wildly. (ANI)