Study finds many heavy elements are created when neutron stars collide

Scientists know that elements lighter than iron are typically forged deep in the core of stars. The extremely high temperature in the core of stars can fuse protons allowing them to be smashed together, resulting in progressively heavier elements. One thing that has stumped scientists is what process creates heavy elements such as gold, platinum, and others.

The mystery surrounding the creation of heavy elements has to do with the fact that the formation of elements of the type requires more energy than stars produce. Researchers from MIT and the University of New Hampshire have determined that out of two suspected sources for heavy metals, one of the long-suspected sources is more prolific at creating heavy elements than the other. Over the last 2.5 billion years, more heavy elements were produced by binary neutron star mergers than by mergers between a neutron star and a black hole.

The study is the first to compare the difference in heavy element production between collisions of neutron stars and a collision between a black hole and a neutron star. Study results suggest binary neutron stars are the most likely source for gold, platinum, and other heavy metals. Researchers also believe the new data could help determine the rate of heavy metal production around the universe.

Project scientists say that stars are efficient at producing lighter elements ranging from hydrogen to iron. However, things get more complicated and require more energy when fusing more than 26 protons, which is the number found in iron. To build heavier elements, there has to be another method for mashing protons together. In 2017, scientists observed a binary star merger using LIGO and Virgo gravitational wave observatories for the first time.

Those detectors discovered gravitational waves originating 130 million light-years from Earth due to a collision between neutron stars. During that merger, a bright flash of light was emitted that contained heavy metal signatures. Incredibly, project researchers say the amount of gold produced during the merger was several times the mass of our entire planet. That event "changed the picture," showing that binary neutron stars merging is the most efficient way to create heavy elements compared to supernova.