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Neutron star collisions and kilonovae

A neutron star collision occurs when two neutron stars—the ultra-dense cores left behind by massive stars—spiral inward and merge together. The collision releases tremendous energy across the universe in multiple forms. When they collide, the merger creates a kilonova, a bright transient explosion powered by radioactive decay of heavy elements produced in the extreme conditions. This matters because neutron star collisions are one of the universe's primary factories for creating heavy elements like gold and platinum, accounting for around half of the isotopes in elements heavier than iron. The 2017 detection of gravitational waves and light from the neutron star merger GW170817 confirmed this theory and opened a new window for studying the cosmos.

Sources

• en.wikipedia.org: “A neutron star merger is the stellar collision of neutron stars. When two neutron stars fall into mutual orbit, they gradually spiral inward due to the loss of energy emitted as gravitational radiation.”
• en.wikipedia.org: “The mergers also produce kilonovae, which are transient sources of isotropic, longer-wave electromagnetic radiation due to the radioactive decay of heavy r-process nuclei that are produced and ejected during the merger process.”
• en.wikipedia.org: “The merger of neutron stars momentarily creates an environment of such extreme neutron flux that the r-process can occur. This reaction accounts for the nucleosynthesis of around half of the isotopes in elements heavier than iron.”