A neutron star forms when the core of a massive star runs out of fuel and collapses. When two neutron stars orbit each other, they will eventually spiral inward and merge, producing a powerful explosion called a short gamma-ray burst as they collapse into a black hole. But before they disappear behind an event horizon, the merged neutron stars may briefly exist as a fast-spinning mega neutron star. In the flickering gamma rays seen in two bursts, astronomers have detected a pattern that indicate