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Homework Help: The origin of some elements

  1. Aug 15, 2012 #1
    By choosing among the following five options, what is the main source in the universe for the origin of the elements : silicon, lithium, bismuth, nickel and uranium?

    Primordial nucleosynthesis – fusion in core of low-mass stars – fusion in core of high-mass stars – slow neutron capture in high mass-stars - rapid neutron capture in supernovae.

    The following is what I think is the right answer but I'd like to be confirmed.

    silicon = Fusion in core of low-mass star
    lithium = Primordial nucleosynthesis
    bismuth = Low neutron capture in high mass-stars
    nickel = Fusion in core of low-mass star
    uranium = Rapid neutron capture in supernovae

  2. jcsd
  3. Aug 15, 2012 #2


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    Bismuth and nickel both have atomic numbers greater than that of iron. So...you might want to re-evaluate your answers for those.

    You are correct that lithium is produced in trace amounts during big bang nucleosynthesis. Whether this was the *main* source of lithium in the universe, I admit that I am not sure of. It certainly seems like stars produce carbon and oxygen directly from helium fusion, by means of the triple-alpha process, leaving it an open question (to me) by what other natural processes light elements like lithium would be produced aside from in the early universe.

    You're right that uranium definitely requires supernovae to produce it.

    I'm not sure what you're calling "low mass" vs. "high mass", but bear in mind that anything that will end as a white dwarf isn't going to be producing silicon in its core. A star has to be *several* solar masses (like 8-10) just to get hot enough for carbon fusion to ignite in the core: otherwise carbon and oxygen are the end of the line (they certainly will be for the sun). I may have said too much already: I don't want to give you answers to things that you should know.
    Last edited: Aug 15, 2012
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