This supercomputer simulation shows one of the most intense cosmic processes: the merger of two neutron stars into a black hole. When a star between eight and thirty times the mass of the sun explodes as a supernova, the compact core left behind is known as a neutron star. A neutron star has a mass that is around 1.5 times that of the sun, compressed into a 12-mile-diameter ball. We witness a pair of neutron stars with masses of 1.4 and 1.7 solar masses when the simulation first starts. Only about 11 miles separate them, which is a little less than their respective diameters. Areas with lower densities were indicated by redder colours.

As the stars spiral to one another, piercing currents start to compress them, possibly fracturing their layers.

Although their outer layers are relatively thin, neutron stars have tremendous densities that are a million times more dense than gold. Their cores crush things far more thoroughly, increasing densities by a factor of 100 million. Consider that a cubic centimetre of neutron star material weighs more than Mount Everest to put such mind-boggling density into perspective. Gamma-ray bursts are thought to be caused by neutron star fusions like this one, according to scientists (GRBs). In just under two seconds, short GRBs produce as much energy as all the stars in our galaxy do in a year.

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