A flash from a distant cosmic collision reveals how the universe forges heavy elements

A gamma-ray burst (GRB), one of the most energetic explosions in the universe, was first detected by the Fermi Gamma-ray Space Telescope in 2023. Short GRBs occur when two neutron stars spiral together under gravity and collide. A neutron star is the extremely dense, collapsed core of a massive star left behind after a supernova explosion.

Using the Chandra X-ray Observatory and Hubble Space Telescope, astronomers traced the exact location of the burst to a very faint galaxy about 8.5 billion light-years away. This burst, named GRB 230906A, occurred inside a stream of debris created when galaxies collide. Such a long stream of material, pulled from galaxies during collisions, is called a tidal tail — and this is where the burst took place.

The neutron star merger also produced a kilonova, a bright explosion that occurs during these collisions. The merger triggered nuclear reactions that synthesized heavy metals through a process called r-process nucleosynthesis. Elements such as gold, platinum, uranium, and other heavy elements were formed and ejected into space. Future stars can form from this enriched material, and events like these may explain the origin of gold on Earth. In about 4–5 billion years, our Milky Way will collide with the Andromeda Galaxy, potentially producing neutron stars that could merge and generate similar bursts.