Question about stellar nucleosynthesis from a non-expert

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Discussion Overview

The discussion revolves around the production of uranium through stellar nucleosynthesis, particularly focusing on the role of supernovae and neutron star mergers. Participants explore the mechanisms involved in the r-process and the evidence supporting these processes in astronomical observations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the minimum number of supernovae required to produce uranium, considering the age of the universe and the solar system.
  • Another participant suggests that uranium is primarily produced by merging neutron stars rather than core collapse supernovae, inviting comments on this perspective.
  • A participant cites Wikipedia to assert that the r-process can occur in supernovae, indicating that only one supernova may be sufficient for uranium production.
  • There is a request for evidence regarding the r-process elements being observed in supernova spectra, particularly for elements heavier than curium.
  • One participant confirms that heavy elements are frequently observed in supernova spectra and provides a reference to support this claim, while expressing uncertainty about the initial composition of the stars involved.
  • Another participant notes that a hypothesis regarding californium powering supernovae was not confirmed and attributes the phenomenon to nickel-56 instead.

Areas of Agreement / Disagreement

Participants express differing views on the primary sources of uranium production, with some supporting the role of supernovae and others advocating for neutron star mergers. The discussion remains unresolved regarding the specifics of these processes and the evidence for them.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about stellar compositions and the conditions under which the r-process occurs. The evidence cited is based on observational studies, but the specifics of these observations and their interpretations are not fully explored.

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Given that the universe is 13.8 billion years old and our solar system is 4.6 billion years old, less than 10 billion years of star birth, life, and death is necessary to produce the heaviest occurring natural elements. Given what we know about supernova, what is the minimum number of supernova required to produce the element uranium?
 
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Wow! That's quite remarkable. Thanks for your reply.
 
Reading the wikipedia article about the r-process leades me to believe that uranium is mostly produced by merging neutron stars, not core collapse supernovae. Anyone have any comments about this?
 
It's probably right. Just not the question that was asked.
 
Looks like the answer is in fact 1, as mentioned above. Rationale, from Wikipedia:

"The creation of free neutrons by electron capture during the rapid collapse to high density of a supernova core along with quick assembly of some neutron-rich seed nuclei makes the r-process a primary nucleosynthesis process, meaning a process that can occur even in a star initially of pure H and He, ..."
 
dtowne said:
Looks like the answer is in fact 1, as mentioned above. Rationale, from Wikipedia:

"The creation of free neutrons by electron capture during the rapid collapse to high density of a supernova core along with quick assembly of some neutron-rich seed nuclei makes the r-process a primary nucleosynthesis process, meaning a process that can occur even in a star initially of pure H and He, ..."
Is there any evidence that this actually happens?
As in, r-process elements actually observed in supernova spectrum, and elements plainly showing they are newly formed (past curium)?
 
Yes, heavy elements show up in supernova spectra all the time. Basically the first search result that I got was http://adsabs.harvard.edu/full/1956PASP...68..296B, and I know I've seen others.

Whether or not those are stars that were initially "pure H and He" I don't know, but there's a reasonable probability you could find out if you dig. There's lots of information on this; supernova are rather well studied.
 
dtowne said:
Yes, heavy elements show up in supernova spectra all the time. Basically the first search result that I got was http://adsabs.harvard.edu/full/1956PASP...68..296B, and I know I've seen others.
Except the hypothesis of Cf powering supernovae was not confirmed when checked, and it is now attributed to Ni-56 instead.
 

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