WASHINGTON—Astronomers have observed the most massive known example of an object called a neutron star, one classified as a “black widow” that got particularly hefty by gobbling up most of the mass of a stellar companion trapped in an unhappy cosmic marriage. The researchers said the neutron star, wildly spinning at 707 times per second,…

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…

Our universe is not as peaceful as what we see in the night sky. Eruptions or catastrophes can happen anywhere at any second. This time, astronomers may have detected a giant gamma-ray flare from a nearby magnetar. A magnetar is a rapidly spinning type of neutron star, which is the remains of a star that…