Colliding neutron stars revealed as source of all the gold in the universe

The late astronomer Carl Sagan once said we are all made of star stuff, which is both accurate and awesome. It turns out gold (and other very heavy elements) are made of neutron star stuff. Researchers at the Harvard-Smithsonian Center for Astrophysics have found that neutron star collisions are the most likely source of these elements in the universe.

Science now holds that all matter in the early universe was hydrogen, which is the fuel of stars. As the first balls of hydrogen condensed into the nuclear furnaces we know as stars, they began fusing hydrogen into helium. This is what young stars do to this day. As stars age, they begin fusing heavier elements as the supply of hydrogen runs out. A red giant can fuse elements up through carbon. For heavier elements, you need a big boom. A supernova will do nicely. When a star dies, it can create elements as large as iron. Now we know where the heavier ones come from. Here’s a little primer on the physics involved:

Scientists have long suspected that a very large explosion would be needed to fuse heavier elements like gold, platinum, uranium, and all the rest. The nature of that process was unclear until now. The Harvard-Smithsonian Center analysis shows colliding neutron stars have probably made all the elements in the universe heavier than iron.

A neutron star is formed when a star a few times larger than the sun runs out of fuel. It collapses in on itself, but isn’t massive enough to form a black hole. Many star systems are at least binary, so it’s possible there are plenty of opportunities for multiple neutron stars to be in close proximity to each other. The massive energy released by the collision fuses heavy elements and also creates a new black hole as the mass of the neutron stars is combined.

The next time you hear about the price of gold, just think for a second where it came from. Each neutron star collision produces many times more of the shiny metal than exists on Earth.


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