NASA has released a stirring animation depicting the theoretical merger of two neutron stars. Once the stars merge, they form a black hole.

Neutron stars are super-dense remnants of dead high-mass stars. As the name suggests, they are comprised entirely of neutrons, which formed from the merging of protons and electrons during the gravitational collapse of a dying star’s core. Neutron stars have a theoretical upper limit to their mass, beyond which the rules of quantum physics dictate that the stars collapse into black holes. A merger is one way to have a neutron star exceed its theoretical mass limit.

Such mergers would release an enormous amount of energy, which could explain the origin of gamma ray bursts—mysterious flares of ultra-high energy that emanate from deep space.