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Questions tagged [nucleosynthesis]

Nucleosynthesis is the process by which stars create heavier elements from hydrogen and helium

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BBN: How is the expansion rate related to the freeze-out of Neutrons?

I've been making my way through several papers and textbooks on the subject, but they all seem to gloss over this subject: how is the equilibrium of protons, neutrons and photons related to the ...
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Where do large deposits of heavy elements come from?

I understand that the heavier elements were produced by a series of fusion reactions in a series of stars. What I've never understood is why the atoms of these elements would ever coalesce together ...
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What is the current measured (i.e. model independent) density of hydrogen $H$ in the universe?

The question came up in this thread: What is the current value for the temperature at which Recombination took place? I was under the impression that we had an independent measurement of Hydrogen in ...
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49 views

How large was the universe at the start of BBN? How large was it after?

I'm trying to get a handle on the basics of BBN. I've read several authors quote the figure of 17 minutes. So BBN started at 3 minutes and ended at 20 minutes after the start of time. So how large ...
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How to calculate angular momentum given angular distribution

I have recently attended a colloquium on transfer reactions. At one point, the speaker was talking about calculating the angular momentum of a nuclear transfer reaction from an angular distribution ...
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Why is hydrogen the most abundant element in the Universe?

Hydrogen is the most abundant element in nature. Does cosmological nucleosynthesis provide an explanation for why is this the case? Is the explanation quantitatively precise?
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Why did CMB decouple when neutral atoms formed?

Atoms can absorb and emit photons. But it is said that when the neutral atoms were first formed the photons got decoupled. If the atom-photon interaction is allowed how can we say that photons were ...
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Why do the sun and planets differ in their chemical elements composition?

The chemical elements composition of the sun changes as its nuclear furnace changes elements into heavier ones. But it is supposed to be mostly Hydrogen at the start. The planets are too cold for ...
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How likely is it that the mass of all humans was generated by the same supernova? [duplicate]

All humans are brothers. They came from the same supernova. ─ Allan Sandage (1926 - 2010) My gut (not a physicist) says not very likely at all. That being said, he was probably referring to ...
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116 views

About what 'time' in the Universe's history did the r-process and s-process begin respectively?

I was reading about this but there is something for which I haven't found a reliable source yet. When did each process begin and is there any estimation of the abundances of the elements throughout ...
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81 views

Does the annihilation of antihydrogen with heavier matter resulting in conversion of heavier elements back to hydrogen?

If an antihydrogen atom annihilate with a heavier atom of matter, will the remaining nucleus of the heavier atom be disassembled into individual protons and neutrons? If so, is this considered to be ...
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The PPI Chain is composed of 3 steps: Does only the 2nd step release energy?

The PPI chain is \begin{align} \rm\ ^1H + {}^1H &\rm\rightarrow {}^2D + e^+ + \nu_e \tag 1 \\ \rm\ ^2D + {}^1H &\rm\rightarrow {}^3He + \gamma \tag 2 \\ \rm\ ^3He + {}^3He &\rm\rightarrow {...
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Can stellar nucleosynthesis processes other than deuterium-lithium, i.e., oxygen-burning, take place in a reactor?

It is known that gravitational confinement and supernovae facilitate the synthesis of heavy nuclides; and, that magnetic confinement is thought to facilitate the deuterium-lithium fusion in human-...
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Why does the H-burning Shell do the CNO cycle instead of the PP Chain?

A star that initially produces energy through the PP Chain will eventually exhaust its Hydrogen leading to a core contraction in order to increase the temperature to generate again nuclear reactions. ...
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What is a Coulomb suppressed reaction?

I have specifically been reading the in context of Big Bang Nucleosynthesis however, I feel the concept is more general. I could not find a definition online, I am just not sure what it means. Many ...
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Why does stellar nucleosynthesis not turn lithium into boron

Another discussion on this site (Why is there a scarcity of lithium?) as well as the wikipedia page on Lithium burning (https://en.wikipedia.org/wiki/Lithium_burning), have helped me understand why ...
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Why can't barium be produced in a supernova explosion?

In this video, Michael Merrifield claims that the elements barium, lanthanum and cerium cannot be produced within supernova explosions, and that they must be produced via a slower neutron-aggregation-...
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Rates of reaction and the expansion of the universe

In Moore, 2013 the following statement is given about reaction rates and the expansion of the universe (my wording): For a reaction to occur we need a rate corresponding to at least one reaction ...
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Could quasars produce elements heavier than oxygen?

I have read that supernovae are the main producers of elements heavier than oxygen. I just wonder whether quasars, which have been around a long time just like supernovae have, could have had a ...
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78 views

Fusion inside a planet with high concentration of radioactive elements?

If an Earth-sized or larger planet had sufficiently large amounts of radium, thorium or uranium, couldn't the resulting fission trigger periodic fusion of hydrogen? I'm thinking of fission happening ...
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Could there be a rocky star, made from silicon, oxygen, etc?

Rocky in terms that it will have mostly silicon and oxygen composition, just like terrestrial planets. But not because it runs out of hydrogen and helium, rather it should start it's life by fusing ...
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Tunneling for hydrogen fusion

So I'm trying to find a rough estimate of the temperature required for Hydrogen to turn into Helium through quantum tunneling. In the lecture we were presented with the following: $$\frac{p^{2}}{2\mu}=...
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How do scientists know Iron-60 is created during supernovae?

I know that the meteoroids contain Ni-60, which is formed after decaying Fe-60, and as per my study, I got to know that Fe-60 is formed during the time of a supernova. But I wonder how scientists know/...
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What about energy in neutron capture?

I have a problem with energy conservation in the neutron capture process. As far as I understood the matter, elements heavier than iron can not be produced in a fusion process, because after ion, ...
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4answers
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How are we stardust?

I am a layperson and certainly not a physics student, though I'm sure that is palpably obvious. I have a strong appreciation for people like Carl Sagan, Lawrence Krauss, and Sean Carrol. I'm often ...
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Matter and antimatter ratio

My question is about the creation of the Universe. The current theory I know is that matter is the debris left after matter/antimatter annihilation at the dawn of the Universe. The question is, wouldn'...
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Why doesn't Dark Matter participate in BBN reactions?

This is a slightly different variation on an earlier question: In the very early universe, the hot plasma consisted of fixed amount of radiation (photons and neutrinos) and matter (electrons, protons,...
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Nucleosynthesis of Tantalum-isomer $^{180{\rm m1}}{\rm Ta}$?

How does nucleosynthesis explain the creation of Tantalum-isomer $^{180{\rm m1}}{\rm Ta}$? Or what is the best theory to explain the existence of this? It must be noted that the Tantalum-isotope $^{...
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How early did primordial oxygen form?

It has been suggested liquid water could exist 10-17 million years after the Big Bang, warmed by the CMB instead of stars. Would Big Bang nucleosynthesis produce oxygen that soon? (Empirically, the ...
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170 views

Can we determine the origin of the universe?

I'm not a fan of religious theories, but I keep asking myself all these following questions: Assume that nothing is created, everything is transformed and the big bang at the end of the period of ...
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1answer
460 views

Why is carbon-12 stable while beryllium-8 is not?

I'm currently studying the alpha process, specifically the triple alpha process. I understand why helium-4 is stable, and why beryllium-8 'prefers' to split into two helium-4 atoms. I also understand ...
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Given this graph from Wikipedia concerning the cosmogenic origin of each element, how are Lithium, Beryllium, and Boron formed from cosmic rays? [duplicate]

So I found this article from another answer, and it's math is way above me but the gist is that some elements heavier than Iron can form in a star, but this path is not the primary source of these ...
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130 views

Qualitative picture or reference for a Lemaître's Cold Big Bang theory

Warning: please, consider this question to be motivated by historical curiosity or as an exercise in model-building. I believe this cannot be considered non-mainstream physics as it was very much ...
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${^{180}}\mathrm{Ta}^\mathrm{m}$ and absent stable species

Writing a piece for laymen which happens to mention nucleosynthesis, I realise that I do not know the answer to the following question: Are there stable isotopes which do not occur in nature? One ...
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153 views

How are the particles produced at the very early universe?

We know that according the standard model of cosmology $\Lambda {\rm CDM}$, there is a primordial plasma after the inflation. And then we study the non-equilibrium evolution of this plasma such as ...
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598 views

Why beta+- decay occurs?

So nice place to ask question like this here. I have read some basic physics magazine like Newton monthly. There I saw article about nuclei generation in star. I want to know more and found wiki ...
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1answer
244 views

Mass-energy conversion mechanism in supernovas

Fusion of nuclei inside stars switches from exothermic to endothermic for Iron and elements heavier than Iron. Supernovas not only achieve fusion of transuranides (albeit in trace relative quantities),...
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Hydrogen in a glass of water

One of the great Sagan quotes is that we are made of star stuff - meaning the atoms in our bodies were formed from stellar nucleosynthesis. However, what about the hydrogen in a glass of water? Would ...
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1answer
112 views

Will hydrogen die out? [duplicate]

Stars create heavy elements up to iron during their lifetimes, and heavier elements beyond iron during supernova events. Are there any processes which create new hydrogen? If not, will all (or most) ...
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If there are long-lived elements in the Island of stability, why are they not present in Nature?

To my understanding, some (but not many) physicists speculate that the Island of stability may contain long-lived elements, as in a billion or so years. But couldn't we rule that out just by the ...
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1answer
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Nucleosynthesis: other than big bang and supernova

According to many texts, hydrogen and helium and traces of lithium-7 were created in a brief period after the big bang; helium is created through fusion (pp, CNO) in main sequence stars; elements like ...
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1answer
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Does all hydrogen originate from the Big Bang?

I was wondering, if every single hydrogen in the universe originate from the time about ~3 min after the Big Bang. I know there are nuclear fusion processes going on in stars like the pp-chain ...
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Why didn't helium continue to generate after a few minutes post-Big Bang?

Helium stopped generating after a few minutes after the Big Bang, but what made it impossible for its generation to continue?
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149 views

What other particles don't participate in BBN?

This is a follow up to an earlier question. Of the responses I got back, the general sense is that Dark Matter (DM) is a "thermal relic" from an earlier epoch of the universe when temperatures were ...
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Big Bang Nucleosynthesis

In the very early universe, the hot plasma consisted of fixed amount of radiation (photons and neutrinos) and matter (electrons, protons, neutrons, etc). There were many competing reaction taking ...
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Why do stars undergo nuclear fusion?

This might sound silly. But we always talk about nuclear fusion in stars and I have always wondered why this process happens at all. Is it inevitable for fusion to happen at the temperature and ...
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1answer
126 views

Is it possible to create helium atoms by bombarding heavy water with neutrons?

If heavy water is bombarded by neutrons is it possible that any of the deuterium atoms can capture neutrons and transmute to helium atoms? I suspect the more probable event would be knocking protons ...
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2answers
376 views

What is an element's “weight” when talking about “elements heavier than iron” being formed in supernovae

I always hear that elements heavier than iron are formed in supernovae. But, what is taken as an element's weight? I had always believed that this meant any elements with an atomic number greater than ...
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1answer
194 views

What could explain the presence of Promethium in stars? [duplicate]

[This is pretty much a copy and paste job from Technetium question but I wanted to add this one in case there was some other explanation] So, I understand that PM doesn't exist in nature [though, I ...
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767 views

What could explain the presence of Technetium in the spectral lines of stars?

So, I understand that TC doesn't exist in nature [though, I don't know why every reference I see regarding TC says that and then goes on to state that it is found in some stars...] but, if that's the ...