The York University Magazine

Fall 2015

The alumni magazine of York University

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A T E A M O F R E S E A RC H E R S led by York University Associate Professor Patrick Hall has discovered some strange behaviour occurring in distant galaxies. Specifically, they noted several instances of gas that appears to be falling into black holes at a high velocity. "Matter falling into black holes may not sound surprising," says Hall, "but what we found was quite mysterious and was Galactic Appetite York researchers discover gas-eating black holes not predicted by current theories." Astronomers have known for more than a decade that every large galaxy has a supermassive black hole at its centre, with a mass from millions to billions of times larger than that of the sun. Mat- ter around these black holes forms a disc bigger than the Earth's orbit around the sun and hotter than the surface of the sun. These discs of hot gas, called quasars, generate enough light to be seen across the observ- able universe. Using data from two components of a large survey of the night sky, known as the Sloan Digital Sky Survey, Hall and his colleagues found a new type of quasar in which gas seems to be heading away from Earth, and possibly towards the quasar's black hole. "The gas in the disc must eventually fall into the black hole to power the quasar, but it's difficult to confirm that gas is actually inflowing through the disc," says Hall. "What is often seen instead is gas blown away from the black hole by the heat and light of the quasar, heading toward us at PHOTOGRAPHY BY MCKENZIE JAMES 10 The York University Magazine Fall 2015

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