... Behemoth black hole found in an unlikely place . ... black holes . ... Black-hole light show . ... This artist rendition shows an accretion disk swirling around a black hole. ... However, according to new theoretical research from two NASA astrophysicists, the wrenching gravity just outside the outer boundary of a black hole can produce yet another bizarre effect: light echoes. ... Many black holes are surrounded by disks of searing hot gas that whirl around at nearly the speed of light. ...