Talk about a heavy snack. For the first time, astronomers have witnessed a black hole swallowing a neutron star, the most dense object in the universe—all in a split-second gulp. Ten days later they saw the same thing, on the other side of the universe. In both cases, a neutron star—a teaspoon of which would weigh a billion tons—orbits ever closer to that ultimate point of no return, a black hole, until they finally crash together and the neutron star is gone in a gobble. Astronomers witnessed the last 500 orbits before the neutron stars were swallowed, a process that took far less than a minute and briefly generated as much energy as all the visible light in the observable universe. “It was just a big quick (gulp), gone,” said study co-author Patrick Brady, an astrophysicist at the University of Wisconsin Milwaukee. The black hole “gets a nice dinner of …