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Our golden connection to a cosmic explosion


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Scientists think a violent neutron star merger 100 million years ago gave rise to all the gold on Earth. (AFP via Getty Images)


Take a look at the gold in the ring on your finger or a piece of jewelry. You are looking at something that came from a violent event that took place a long time ago in our galaxy before Earth was even born.


The precious metal can only be made during some of the most cataclysmic events in the universe, which is why it is so precious. 


Now, scientists from Columbia University and the University of Florida believe they have found the source of Earth's gold: the collision of two neutron stars that happened 100 million years before our solar system formed that took place roughly 1,000 light years away — which is close in cosmic terms. 


Neutron stars are what you get when a massive star runs out of fuel and collapses, essentially melting together protons and electrons to form neutrons.


The scientists presented their findings, published in the journal Nature, at a recent meeting of the American Astronomical Society in Honolulu. 


Clues contained in ancient meteorites


To calculate the source of Earth's gold, the scientists examined meteorites, which are very old remnants of the pre-solar nebula, the cloud of gas, dust and debris that eventually gave rise to our solar system.  


Radioactive isotopes in the meteorites act as timepieces that trace back to the early solar system when elements were first incorporated. 



As neutron stars collide, some of the debris blasts away in particle jets moving at nearly the speed of light. (NASA's Goddard Space Flight Center/CI Lab)


The scientists compared the quantity of these isotopes, which are elements that come in different masses due to the number of neutrons they contain, to computer models of the amount produced by neutron star mergers. 


They also included data from LIGO, the gravitational-wave observatory that has recorded actual collisions of neutron stars. 


This enabled the scientists to determine the time and distance of the collision, which turned out to be fairly close by. If such a collision happened today 1,000 light years from here, it would outshine all the stars in the sky. 


Explosive dispersal of precious metals


The amount of energy released during these extreme events is so huge, with temperatures so extreme, they become cosmic blast furnaces forging heavy metals such as platinum and gold through nuclear fusion of lighter elements. 


These new elements are then blasted outwards across space where they drift as shrapnel for millions or billions of years until they encounter a new star system being born. 


They are captured by the gravity of the cloud of dust and gas that eventually condenses into a central star and a system of planets — and some leftover space rocks. The gold ends up spread around the planets like candy sprinkles on a cake. 



This is why gold is so rare. These neutron star collisions only happen every 100,000 years or so in our galaxy. 


Not everyone agrees with this scenario because supernovae, giant stars that end their lives in powerful explosions, also produce gold, and they happen more frequently, every 50 years or so. So it's possible that Earth's gold is a blend of both. 


Behold the cosmic bomb in Earth's gold


So the next time you hold a piece of gold jewelry, look at the metal closely and think about the fact that it is older than life, older than Earth and the sun. 

It was blown out of an unimaginably violent event, drifted among the stars of the Milky Way for 100 million years, then became part of the birth of our baby solar system. 


Now we dig it out of the ground or pan for nuggets in rivers and form it into ornamental shapes that you can hold in the palm of your hand

That's quite a journey. 


It is something wondrous to think about during these troubled times.




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