Neutron stars merging. Neutron stars are the remnants of stars that have run out of fuel and exploded as supernova, eventually collapsing into a superdense core. A typical neutron star has a mass of between 1.3 and 2.1 solar masses but measures only 10km in diameter. Neutron stars can exist as paired, or binary, stars. This illustration shows the collision of two neutron stars at the very final stage, just before they fully merge. This causes a violent burst of magnetic radiation lasting milliseconds, as well as the emission of gravitational waves. It is suggested that this is the source of short gamma ray bursts.© MARK GARLICK/SCIENCE PHOTO LIBRARY—Getty Images/Science Photo Library The strongest material in the universe has been discovered: nuclear pasta from neutron stars. The material is so intense it could never exist on Earth—if somehow a tiny amount were transported here, it would explode like a nuclear bomb.Instead, it can be found deep inside the crust of the smallest, densest known stars, scientists have discovered via computer simulations.