So the iron in our blood had to have come from an ancient star that went supernova many billions of years ago. Our sun is estimated at 4.6 billion years, so it had to be some point before that, probably billions of years earlier. And not all of it comes form the same exploding star. Some could be from a star that exploded 6 billion years ago, some form a star that exploded 10 billion years. There also could be some that found it's way to our solar system from a star that exploded just 2 billion years ago, and those particles drifted her or hitchhiked on something else to reach Earth. But they all came from massive stars that went supernova.
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poldi say: All elements heavier than oxygen were formed in the interior of stars.
When they explode, they eject the elements they have been creating through various levels of fusion back into space.
The material becomes part of the clouds of dust and gas that then become the next generation of stars and planets (like the Earth).
The iron in our blood comes from iron in the Earth.
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Tom S say: Yes, all elements heavier than lithium "came from a star(s) that blew up more than 4 billion (closer to 10 billion) years ago"
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quantumclaustrophobe say: It does... all elements heavier than Carbon come from huge stars that lived, died, and exploded long ago. Iron is the *heaviest* element that can be produced within the core of a star, while releasing energy; once iron begins to be produced, the star will soon be exploding... Since we have iron on Earth, that means that stars had to live and die long before our solar system was formed in order for those elements to appear here.
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ANDY say: In the beginning, the only elements present in the universe were hydrogen and helium─90% hydrogen and 10% Helium.
When stars formed, and followed by the creation of galaxies, the death of stars, those with heavy masses, developed the heavier elements that were not present before─supernovae is the name given to the explosion of those massive stars.