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Just came across this, didn't see it posted elsewhere. Could be significant in our stellar evolution models. (?)
http://physicsweb.org/articles/news/9/1/8
http://physicsweb.org/articles/news/9/1/8
The sensitivity, yes. But, a change in reaction rate as described would and/or could still have a significant affect on supernova models / rates. It doesn't affect main sequence stars anyway, just cores over 100 million K; ie, red giants.Nereid said:AFAIK, the great sensitivity of this process to temperature has been known for a long time. I would guess (and it is just a guess) that solar (and stellar) models are built with the reaction cross-sections as inputs, and that the models are run with at least the full range of values as determined experimentally.
Many PRs and popular press articles, IMHO, contain 'marketing fluff' (shall we say) - not enough to trigger a law suit under any 'truth in advertising' rule maybe, but ...
Nereid said:I would guess (and it is just a guess) that solar (and stellar) models are built with the reaction cross-sections as inputs, and that the models are run with at least the full range of values as determined experimentally.
Which?franznietzsche said:In all the papers I've read on solar models (one of which I've worked with directly) I've never seen this to be the case.Nereid said:I would guess (and it is just a guess) that solar (and stellar) models are built with the reaction cross-sections as inputs, and that the models are run with at least the full range of values as determined experimentally.
I would say "b" above is used often except that the values are determined mathematically rather than experimentally. But, the original post (link) seems to indicate that the "full range" has to be re-defined, so models would change also.Nereid said:Which?
a) reaction cross-sections built in?
b) run with at least the full range of values as determined experimentally?
c) both the above?
d) something else??
A change in the Triple-Alpha process would have nothing at all to do with the so-called solar neutrino problem. That "problem" (since solved) arose from calculations on the output of the Proton-Proton Chain process by which most H in our sun is converted into He. Triple-Alpha is not going on at all until He can fuse into C and O (mostly) above at least 100 million K and several billion years from now.Nereid said:IIRC, one strand of the work done during the decades' long investigation of the solar neutrino problem was to see how much variation in neutrino output (of the solar models) was possible, within the (extended) range of experimental cross sections.
The triple-alpha process is a nuclear fusion reaction that occurs in the cores of stars. It involves the fusion of three helium-4 nuclei (alpha particles) to form a carbon-12 nucleus.
The triple-alpha process converts three helium nuclei into one carbon nucleus. This changes the ratio of helium to carbon in the star, as well as other elements that are created through subsequent nuclear reactions.
The triple-alpha process requires extremely high temperatures and pressures, such as those found in the cores of stars. It also requires a sufficient abundance of helium and other elements to sustain the reaction.
The triple-alpha process is one of the primary sources of energy production in stars. It releases a large amount of energy through the fusion of helium nuclei, which helps to sustain the star's core temperature and prevent collapse.
The triple-alpha process is most commonly observed in low-mass stars, but it can also occur in more massive stars under certain conditions. However, the rate of the reaction may differ depending on the size and composition of the star.