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This undated composite image provided by Lynette Cook and Andrea Ghez via the journal Nature shows an image of the center of our Galaxy from laser-guide-star adaptive optics on the Keck Telescope. More massive black holes have larger event horizons, the region within which even light can not escape. If a ten billion solar mass black hole resided at the Galactic center, its immense event horizon would be visible (illustrated by the central black disk). The actual black hole at the Galactic center is 2500 times smaller. (AP Photo/Lynette Cook and Andrea Ghez via Nature)

Amazing black holes detected

Two X-ray space observatories, NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's XMM-Newton, have teamed up to measure definitively, for the first time, the spin rate of a black hole with a mass 2 million times that of our sun. (NASA)