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Ars Technica: Quasi-stellar radio sources, or "quasars," are supermassive black holes, found at the center of galaxies, that produce extreme amounts of light as they pull material into themselves. The material swirling around the black holes is much brighter than the starlight of their host galaxies and can be up to 100 times brighter than all the stars in the Milky Way put together. That brightness disparity makes it hard to study quasars and to look past them to study their host galaxies. However, the difference in brightness is much less in certain areas of the spectrum. C. Megan Urry of Yale University and her colleagues used a near-IR camera on the Hubble Space Telescope to examine 11 quasars, all roughly 12 billion light-years away. They were selected because each is partially obscured by dust, which further reduces the brightness disparity. Urry's team found that all 11 of the host galaxies were undergoing collisions with other galaxies. That discovery supports the theory that galactic collisions drive the feeding of the black holes by disrupting the material surrounding them.