The fragments thrown after the collision of a pair of neutron stars not only synthesize stable elements such as gold and silver, but also synthesize a large number of radioactive elements. They will decay, fission, release a lot of energy, and heat the fragments themselves to make them glow. It is not as bright as a supernova, but it can reach about one thousand times the brightness of a new star, so it is called a thousand stars. In August 2017, astronomers first observed the gravitational waves emitted before and after the merger of a double neutron star, and found it about 10 hours later The phenomenon of neutron star fragments formed by the neutron star has completely confirmed the conjecture that neutron star mergers can synthesize a large number of heavy elements. It can be inferred from this:. ['Supernova is brighter than nova.', 'Gravitational waves can release a lot of energy.', 'Thousands of stars contain large amounts of gold and silver.', 'Heavy elements in the universe are produced by the collision of neutron stars.']