National Aeronautics and Space Administration

When and how did the elements of life in the Universe arise?

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 upon which those molecules might combine to form life?

All elements heavier than hydrogen and helium are manufactured inside stars, or produced when a star’s life ends as a supernova.  NASA seeks to study the way stars evolve over time, and how they end their lives in order to learn about how the Universe has transformed itself from a place of only two simple elements to one with a molecular complexity sufficient to support life.

Understanding how stars form, how they evolve over their lives, and how they die, is key to understanding the history of heavy elements in the Universe.  By studying stellar nurseries in which stars are born as well as the supernovae, debris shells, white dwarves, and neutron stars left behind when they die will reveal how the Universe has created and disseminated complex elements throughout its history. This will permit us to predict when there was a sufficient quantity of these elements such that life creation would have been possible.  Knowing when the Universe was capable of supporting life will help us evaluate the likelihood that other life exists in the cosmos.