Cosmic Gold: Neutron Star Collisions Forge Enough Precious Metal for Dozens of Earths

Scientists now have strong evidence that the universe's "gold factories" are collisions between neutron stars, capable of producing enough of the precious metal to form dozens of Earth-mass planets. This groundbreaking understanding stems from the observation of GW170817, a neutron star merger detected on August 17, 2017.

For years, astrophysicists knew that heavy elements like gold, platinum, and uranium are forged in extreme cosmic conditions through a rapid neutron-capture process, or r-process. Initially, scientists suspected that supernova explosions were the primary source. However, calculations indicated that supernovae alone could not account for the abundance of these heavy elements observed throughout the universe.

The GW170817 event provided the missing piece of the puzzle. Detected by the LIGO and Virgo gravitational wave observatories, the merger occurred in the galaxy NGC 4993, approximately 130 million light-years away. The signal was unique, lasting nearly two minutes, with the neutron stars orbiting each other thousands of times before colliding. Crucially, just 1.7 seconds after the gravitational waves were detected, satellites registered a gamma-ray burst, followed about 11 hours later by a kilonova – an explosion caused by neutron-rich material ejected during the merger.

This kilonova was observed by around 70 observatories worldwide and space telescopes. Analyses confirmed that such collisions generate immense quantities of heavy elements, including gold. Professor Dorota Gondek-Rosińska from the University of Warsaw explained that the mass of gold produced in this single event could be equivalent to tens of Earth masses.

Despite the immense gold production, Professor Gondek-Rosińska noted that it is highly improbable for significant new amounts of gold to reach Earth. The gold already present on our planet arrived billions of years ago through meteorite impacts. While neutron star collisions are common across the universe, they occur very rarely within a single galaxy, estimated at once every few hundred million years.