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My question is this: If iron fusion seems to be the last step in stellar life, then where did we get all the heavier elements on earth? My understanding is that all of the elements on earth heavier than helium were produced in stellar furnaces. - Star ash.

All of the post-iron elements are formed in supernova explosions themselves. So much energy is released during a supernova explosion that the freed energy and copious free neutrons streaming from the collapsing core drive massive fusion reactions, long past the formation of iron. Sure, this absorbs a lot of energy, but there's plenty available once the explosion has begun.

I guess statistically speaking the heavier elements are much rarer than oxygen, carbon, nitrogen, etc, but does this mean that maybe life is truly really rare (except in our neck of the Milky Way)?

That's right. Supernova nucleosynthesis isn't as efficient as the long years of synthesis in stellar cores.

Have elements heavier than Iron ever been detected outside our Solar System (Like in the emission lines of a nebula, for example - or does the physics model predect them?)

Absolutely. They're everywhere.

This page was last updated June 27, 2015.

About the Author

Dave Kornreich

Dave was the founder of Ask an Astronomer. He got his PhD from Cornell in 2001 and is now an assistant professor in the Department of Physics and Physical Science at Humboldt State University in California. There he runs his own version of Ask the Astronomer. He also helps us out with the odd cosmology question.

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