Where We Come From

Ever wonder where we really came from? Washington University graduate student Cole D. Pruitt explains the connection between the world around us, burping stars and nuclear pasta.

About the scientist

Cole is a graduate student in nuclear chemistry in Arts & Sciences at Washington University and also the co-director of a documentary about the game of Go called “The Surrounding Game.” Screen Shot 2015-09-02 at 4.29.13 PM
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  1. Matt S says:

    Interesting. But are you saying that K and Ca aren’t made in regular stars even though they are smaller than iron Also, does anyone think that there was a super nova (or more than one) near here in order to create the other elements we find?

  2. Cole D. Pruitt says:

    Hi Matt,

    This is Cole Pruitt from the video. You pose two excellent questions!

    You’re correct that potassium (K) and calcium (Ca) have lower atomic numbers than iron (Fe) does, and our current understanding of massive, pre-supernova stars suggests that a tiny amount of K and Ca is created in these stars, too. But this story is a little more complicated than I suggested in the video: the star may include all elements up to iron, but elements with unusually-stable isotopes (helium, carbon, oxygen, silicon, and iron, among others) will dominate the star’s composition. This is roughly similar to the idea of chemical equilibrium: while there is always a tiny fraction of all the nuclear ‘reactants’ present, the equilibrium is shifted heavily toward the more stable isotopes so that very little K and Ca would be present before the supernova.

    As an aside, supernovae are not the only source of higher-element nucleosynthesis. X-ray bursts, novae, and even neutron star mergers may also contribute substantially to the nuclei in the cosmos (but three minutes isn’t enough time to cover all of these topics). Certainly, predicting the changes of isotopic composition of stars and the cosmos remains active area of research in the nuclear and astrophysics communities.

    And yes – it’s presumed that a supernova in the distant past seeded the solar system with a variety of elements. Right now, it’s the only feasible process that could produce extremely heavily elements like uranium and gold that we find on Earth today. Finding the source of that supernova is a lot more difficult, but it doesn’t mean people aren’t looking.

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