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Questions tagged [nucleosynthesis]

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

Nucleosynthesis is the process by which stars create heavier elements from hydrogen and helium. This includes the process of fusion which can synthesize up to iron, and if the star has sufficient mass, elements beyond iron through stellar collapse and subsequent nova and supernova explosion.

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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 stellar nucleosynthesis doesn't generally produce a…
Scott Forschler
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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 place and using statistical methods I understand…
user32023
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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 why beryllium-8 and helium-4 form carbon-12.…
evtoh
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Does pressure alter nuclear reaction rates?

I'm studying the nuclear reactions involved in nucleosynthesis. As I understand it, the primary variables are the density of the particles, the cross section of the particle, and the average velocities. At around 1 MeV, we assume that the velocities…
Quark Soup
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How does Dodelson calculate the number density of a particle species?

In chapter three of Modern Cosmology, Dodelson models the evolution of a particle plasma as the universe expands. On page 61, the author gives the formula for the species-dependent equilibrium density as:$$n_i=g_i\space…
Quark Soup
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What are the number densities of neutrinos and positrons during BBN?

I'm attempting to work through the third chapter of Dodelson's Modern Cosmology. He gives an approximation for the neutron-proton conversion rate, $\lambda_{\rm np}$ that he lifted from Bernstein, but doesn't give any of the science behind…
Quark Soup
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What is the proton to neutron ratio at freeze-out?

I'm reading through Dodelson chapter on BBN. I'm trying to follow the examples, but having trouble with the basics. First, the proton to neutron ratio is quoted as: $$\frac{n_p}{n_n}=e^{\frac{Q}{T}}$$ Where Q = 1.293 MeV and T is the temperature…
Quark Soup
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