We are all, as Carl Sagan said, star-dust. You might think that since most stars are pretty much the same, all star-dust is equal. But we have evidence that some star-dust is more equal than others. Yes, some elements seem to have a very special origin: neutron star mergers.
Most stars are pretty much all hydrogen. Near their center, fusion busily turns hydrogen into helium. Eventually, that hydrogen will run out and, like a pub that runs out of beer, the real destruction begins. The star starts turning helium into heavier elements at an increasingly feverish rate. The end, no matter how hot and heavy the star, comes when the star’s core is made of iron.
Up to iron, the process of fusion releases more energy than it consumes. But after iron, fusion consumes more energy than it releases, which essentially shuts the star down. Once this was understood, scientists were left wondering where the remaining 80 odd elements that are heavier than iron came from.
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