• When and how did the elements of life in the Universe arise? - NASA Science
  Following the Big Bang and the gradual cooling of the Universe, the primary constituents of the cosmos were the elements hydrogen and helium. Even today, these two elements make up 98% of the visible matter in the Universe.  Nevertheless, our world and everything it contains—even life itself—is possible only because of the existence of heavier elements such as carbon, nitrogen, oxygen, silicon, iron, and many, many others. How long did it take the first generations of stars to seed our Universe with the heavy elements we see on Earth today?  When in the history of the Universe was there a sufficient supply of heavy elements to allow the formation of prebiotic molecules and terrestrial-like planets
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