Neutron star collisions make gold

For decades, astronomers debated where heavy elements like gold, platinum, and uranium came from — stellar fusion only produces elements up to iron. In 2017, the LIGO gravitational-wave observatory detected a neutron star merger (kilonova) in a galaxy 130 million light-years away. Spectroscopic analysis confirmed that the collision produced approximately 10 Earth-masses of gold. The event also confirmed that gravitational waves travel at exactly the speed of light, as general relativity predicts. All the gold in the wedding ring you might be wearing was forged in a similar collision billions of years ago.

Source: Abbott et al., The Astrophysical Journal Letters (2017)