Supernova and Rare Elements

Some of the rare chemical elements are generated in the supernova explosion. The origin and evolution of life are connected in the most intimate way with the origin and evolution of the stars.

We have relatively abundant gold and uranium on Earth only because many supernova explosions had occurred just before the solar system formed. Would our lives be improved if gold and uranium were as obscure and unimportant on Earth as praseodymium?

The Sun is a second – or third – generation star. All the matter in it, all the matter you see around you, has been through one or two previous cycles of stellar alchemy.

Other planetary systems may have somewhat different amounts of our rare elements. There are planets where the inhabitants proudly display pendants of niobium and bracelets of protactinium, while gold is a laboratory curiosity.

The very matter of which we are composed, the atoms that make life possible, were generated long ago and far away in giant red stars. In fact the relative abundance of the chemical elements found in the Cosmos matches the relative abundance of atoms generated in stars. No doubt, red giants and supernovae are the ovens and crucibles in which matter has been forged.

The existence of certain varieties of heavy atoms on the Earth suggests that there was a nearby supernova explosion shortly before the solar system was formed. But this is unlikely before the solar system was formed and this is unlikely to be a mere coincidence; more likely, the shock wave produced by the supernova compressed interstellar gas and dust and triggered the condensation of the solar system.

When the Sun turned on, its ultraviolet radiation poured into the atmosphere of the Earth; its warmth generated lighting; and these energy sources sparked the complex organic molecules that led to the origin of life.

Life on Earth runs almost exclusively on sunlight. Plants gather the photons and convert solar to chemical energy. Animals parasitize the plants. Farming is simply the methodical harvesting of sunlight, using plants as grudging intermediaries.  We are, almost all of us, solar-powered.

Finally, the hereditary changes called mutations provide the raw material for evolution. Mutations, from which nature selects its new inventory of life forms, are produced in part by cosmic rays – high-energy particles ejected almost at the speed of light in supernovae explosions.

supernovae carl sagan

The evolution of life on Earth is driven by the spectacular death of distant, massive suns. Image: © Megan Jorgensen
 

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