All that glitter in space
There’s too much gold in the universe, No one knows where it came from.
Gold is an element, which can’t be made through chemical reactions — though alchemists tried for centuries. To make the sparkly metal, you have to bind 79 protons and 118 neutrons together to form a single atomic nucleus. That’s an intense nuclear fusion reaction. But such intense fusion doesn’t happen frequently enough, at least not nearby, to make the giant trove of gold we find on Earth and elsewhere in the solar system.
A new study has found the most commonly-theorized origin of gold — collisions between neutron stars — can’t explain gold’s abundance either. So where’s the gold coming from? There are some other possibilities, including supernovas so intense they turn a star inside out. Unfortunately, even such strange phenomena can’t explain how blinged out the local universe is.
Neutron star collisions build gold by briefly smashing protons and neutrons together into atomic nuclei, then spewing those newly-bound heavy nuclei across space. Regular supernovas can’t explain the universe’s gold because stars massive enough to fuse gold before they die — which are rare — become black holes when they explode. And, in a regular supernova, that gold gets sucked into the black hole.
Only in rare cases of magneto-rotational supernova, a dying star spins so fast and is wracked by such strong magnetic fields that it turns itself inside out as it explodes. As it dies, the star shoots white-hot jets of matter into space. And because the star has been turned inside out, its jets are chock full of gold nuclei. Stars that fuse gold at all are rare. Stars that fuse gold then spew it into space like this are even rarer.
But even neutron stars plus magneto-rotational supernovas together can’t explain Earth’s bonanza of gold.Past studies were right that neutron star collisions release a shower of gold. But those studies didn’t account for the rarity of those collisions. It’s hard to precisely estimate how often tiny neutron stars — themselves the ultra-dense remnants of ancient supernovas — slam together. And scientists have seen it happen only once.
Even rough estimates show they don’t collide nearly often enough to have produced all the gold found in the solar system. Though models, scientists have found that neutron star collisions produce strontium, which matches observations of strontium in space after a neutron star collision. Magneto-rotational supernovas did explain the presence of europium in their model, another atom that has proved tricky to explain in the past. But gold remains an enigma.
