Neutron stars merging, supercomputer model. Animation clip 8 of 11 showing two neutron stars green cores merging to produce a black hole. Neutron stars are immensely dense stellar core remnants, formed after a massive star runs out of fuel and its core collapses. This modelling has shown how black hole formation takes place during the merger, with the black hole grey sphere surrounded by super_hot plasma at the end of the clip. The merger is extremely rapid, occurring in milliseconds timer at upper left. The colour_coding key at lower left shows the density of the stellar material, with red indicating lower densities than orange, yellow and green. This merger also produces a gamma_ray burst GRB, not shown, an extremely energetic release of gamma rays. The final two clips in the sequence K003/2670_2660 show the process of neutron star merger and GRB production in greater detail, as modelled by the Damiana supercomputer at Germany磗 Max Planck Institute for Gravitational Physics also called the Albert Einstein Institute or AEI and researchers at the Zuse Institute Berlin ZIB. Animation published in 2011.