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Posted on 09/10/2011 10:57:34 AM PDT by Diana in Wisconsin
(i) Why do predictions of helioseismology disagree with
those of the standard solar model?
(ii) What is the solution to the lithium problem in Big Bang
nucleosynthesis?
(iii) What do the observed light-nuclide and s-process
abundances tell us about convection and dredge-up in
massive stars and AGB stars?
(iv) What are the production sites of the gamma-ray emitting
radioisotopes 26Al, 44Ti and 60Fe?
(v) What is the origin of about 30 rare and neutron-deficient nuclides beyond the iron peak (p-nuclides)?
(vi) What causes core-collapse supernovae to explode?
(vii) What is the extent of neutrino-induced nucleosynthesis?
(viii) What is the extent of the nucleosynthesis in proton-rich outflows in the early ejecta of core-collapse supernovae?
(ix) What are the sites of the r-process?
(x) What causes the discrepancy between models and observations regarding the mass ejected during classical nova outbursts?
(xi) Which are the physical mechanisms driving convective
mixing in novae?
(xii) What are the progenitors of type Ia supernovae?
(xiii) What is the nucleosynthesis endpoint in type I x-ray
bursts? Is there any matter ejected from those systems?
(xiv) What is the impact of stellar mergers on Galactic
chemical abundances?
(xv) What are the production and acceleration sites of
Galactic cosmic rays?
There are plenty of open questions, and that is nice as it gives opportunities to make contributions.
Good points. Most, but not all, of the details you listed I have read - though not the r-process in detail. They have been fundamental in nuclear engineering since Gamow’s first papers in 1937-38. (And he was the author of my primary nuclear engineering texts used in 1974-1978, with more university level classes 1978-1983.) Gold is difficult to “fabricate” because it is on the wrong side (the lowering binding energy side of the curve above the most stable isotopes of Fe and Ni. To make the conventional nucleosynthesis process of gold even more difficult, you must also fabricate neutron-rich isotopes and allow them to decay “down” into all of the elements between U238 and Fe.
The more fundamental problem above these details is resolving the issue about total number of collisions needed to create that final isotope of gold we mine from the earth’s crust. And every isotope of iron, Ca, Ne, Oxygen, Carbon, etc. All these need to be created as well.
But - all of the individual fusion details conceded - they have all been confirmed in the labs, many I have done myself - we can account for between 144,000 and 158,000 tonnes of gold already mined from the earth’s crust. That’s 9.48 x 10^34 gold atoms mined - more, obviously, have been created since the Big Bang but not mined yet.
How do you reconcile the need for more than 3.8 x 10^36 collisions in less than 9 billion (9x10^9) years between the Big Bang and the formation of the solar system? You are requiring more than 10^19 supernova-caused fusions per second for every second for every year for 10^9 years ...
And that assumes every fusion ever happening is 100% production, and that no gold atom is lost between stars as interstellar dust.
Now, after you have “built” all of the gold we have mined, you still need to “build” all of the iron, carbon, nickle, magnesium, calcium, .... Because every supernova-caused fusion of He that went towards building those 10^39 gold isotopes, did not build a single carbon, neon, oxygen, nitrogen, calcium isotope.
Thank you both for this very informative and engaging sidebar!
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