Questions tagged [nucleosynthesis]

Questions to do with how new atomic nuclei are created inside the universe.

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Do the newly-created deuterons in our Sun release any photons? In addition to a positron and an electron neutrino?

Perhaps this is a nuclear physics question, but.... When two colliding protons deep inside our Sun finally turn into a deuterium nucleus or deutron (after approximately ten octillion chances, on ...
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Are there any naked-eye visible stars in our Milky Way that are particularly rich in calcium? (I'm just curious)

There are Calcium-rich supernovae but here I'm asking about stars that one might see in the night sky. I'd like to ask if there are any naked-eye (or binocular-assisted) visible stars in our Milky Way ...
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Can I "see" nucleosynthesis in R Geminorum with a small telescope, a plastic diffraction grating and a cell phone? (famous technetium lines)

R Geminorum is a magnitude +6 to +11 variable star notable for the discovery of technetium spectral lines. As the longest lived isotope is only a few million years, this was direct evidence that ...
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Why is the carbon/oxygen ratio at low metallicities important to study?

Oxygen and carbon are the most abundant elements in the Universe (formed via stellar nucleosynthesis), following only hydrogen and helium (formed via the Big Bang). There seems to be a lot of work to ...
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How sensitive are early universe abundance calculations to the neutron half-life?

Phys.org's Physicists announce the world's most precise measurement of neutron lifetime discusses the accepted for publication Phys. Rev. Letter Improved neutron lifetime measurement with UCNτ (links ...
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Why is it that lithium and deuterium are burned before hydrogen?

Protium ($^1H$) has a nuclear binding energy near 0. Meanwhile, lithium and deuterium have higher binding energies. Why is it that they are burned first (or at lower temperatures)? Is it perhaps ...
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Elements of celestial bodies

Could someone tell me if it proceeds as well as which or which works would allow us to conclude the origin of the elements for different types of bodies or celestial phenomena? Edited: This image was ...
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Is oxygen an alpha element?

Type II (core-collapse) supernovae occur shortly after star formation and enrich a galaxy with $\alpha$ elements such as O, C, NE, Mg, Ca and Si. On the other hand, Type Ia supernovae occur on a more ...
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1 answer
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Spectral lines of the Sun?

If I remember correctly, the pp chain and (partially) the CNO cycle are the dominating set of reactions in our Sun. On the other hand, the composition of the Sun has many more elements/isotopes than ...
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Photodisintegration vs Spallation

Is photodisintegration belongs to a form of spallation? Is photodisintegration only limited to nucleus hit by high energy gamma-ray, whereas the nucleus in spallation can be hit by any ​high energy ...
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2 answers
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Does Alpha Process Produce Bismuth?

In the book "Horizons: exploring the universe-Cengage learning (2018)", p200, it states that: Helium fusion produces carbon, and some of the carbon nuclei absorb helium nuclei to form ...
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1 answer
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Does Oxygen-burning process produce Neon?

In the book "Horizons_ exploring the universe-Cengage learning (2018)", p200, it states that: Helium fusion produces carbon, and some of the carbon nuclei absorb helium nuclei to form ...
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Can someone tell me the contribution of s-, r-, and p-isotope processes to copper?

I have looked for relevant information in the paper Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components before, but unfortunately, it ...
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How do we know or predict which particles were present before Big Bang Nucleosynthesis occurred?

I'm reading Carroll and Ostlie's "An Introduction to Modern Astrophysics". In the BBN section, they describe that the universe contains a mixture of photons, electron-positron pairs, and ...
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Expanded element (and molecule) abundance graph?

There is the "classical" nucleosynthesis timeline chart where the $\log ({\rm mass \,fraction})$ is plotted as a function of $\log(t)$ where $t$ is in seconds after the big bang, looking e.g....
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Why does this nucleogenesis table not label s and r-processes for all elements (not-labmade) past Fe?

I'm reviewing nucleogenenesis and came across the table below. I like it because it actually labels the s and r-process elements, but I became confused as to why the neutron capture processes begin at ...
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14 votes
3 answers
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Formation of elements in the Sun other than helium

I just learned that the Fraunhofer lines of the Sun's spectrum indicate that the Sun contains various elements other than just hydrogen and helium (for example, Na and Fe) but don't the Sun's p-p ...
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2 votes
1 answer
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Would dropping a white dwarf or a "still-hot" stellar core into a large planet or brown dwarf create a star?

In the Wikipedia article about stellar engineering, I found this quote: In The Saga of the Seven Suns, by Kevin J. Anderson, humans are able to convert gas giant planets into stars through the use of ...
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Relation between core mass and red giant mass?

Yes, the title might be confusing (I'd appreciate some more clarification on it :D ). I have an estimated mass of hydrogen in the core of a star, and how much hydrogen will be in the core when the ...
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4 votes
1 answer
171 views

What is the length of time for each fusion process in a massive star?

In a massive star (i.e. an O5 star), first hydrogen is fused into helium, then helium is fused into carbon. This process continues to neon, oxygen, and finally silicon burning. So I am wondering, how ...
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2 votes
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Mass required for a certain fusion process

Suppose we have a density model $$ρ = ρ_c (1-r/R)$$ where $ρ$ is density, ${}_c$ means central, and $R$ is the stellar radius. Let's call the temperature for that fusion process to begin, $T_f$. I ...
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26 votes
1 answer
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Is lithium considered a metal in astronomy?

My lecture notes are conflicting on this issue so I seek definitive clarification. In Astronomy, are metals either A: the elements which form within stars (i.e., not Big Bang nucleosynthesis, where ...
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How can I estimate the initial luminosity of a SNIa given initial mass of Ni-56?

The initial portion (and peak) of a SNIa's light curve is powered by the $\beta$-decay reaction: $$ ^{56}Ni \rightarrow ^{56}Co + e^+ + \nu_e + \gamma $$ Supposing we know how much Ni-56 is created in ...
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15 votes
1 answer
518 views

What effects besides "mass defect" cause the alpha ladder beyond iron-56/nickel-56 to be endothermic?

Many sources state that fusion beyond iron-56/nickel-56 (and certainly beyond nickel-62) is impossible due to them being among the most tightly bound nuclei. For example, in the Wikipedia article on ...
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31 votes
1 answer
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Why don’t supergiants at least start to fuse nickel into even heavier elements before going supernova?

The last primary fusion process to take place in extremely massive stars is silicon burning, where the 28Si produced by oxygen burning is exothermically fused with alpha particle after alpha particle ...
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How scientists estimated the number of near-Earth supernovae over the last 11 million years?

According to this article on wikipedia, An estimated 20 supernova explosions have happened within 300 pc of the Earth over ...
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How did the amount of nuclide produced by s- and r-process changed over time?

For a exercise I need to find out how the amount of nuclide produced by s- and r-process changed over time and I also need to draw a schematic diagram of the s-/r-ratio vs. time from 13.6 Ga till ...
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4 votes
0 answers
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Neutron star r-process nucleosynthesis

The $r$-process in supernovae happens when a high flux of neutrons irradiates the heaviest abundant nuclei (in the region of iron), resulting in endothermic nuclear reactions. To the extent that at ...
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9 votes
1 answer
229 views

What percentage of Helium-3 is primordial vs produced in stars

I tried to research but what I found is pretty limited. A very tiny but non zero percentage of primordial matter was Helium-3 or 3He. Stars produce 3He as part of the proton-proton chain but they ...
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27 votes
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Are we really star-stuff from the interior of collapsing stars?

Carl Sagan has said several times that we are "star-stuff". One instance can be found in Good Reads' Carl Sagan > Quotes > Quotable Quote: The nitrogen in our DNA, the calcium in our teeth, the ...
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15 votes
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Does a star fuse helium to beryllium on the main sequence?

When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron. When the star is fusing to beryllium, will the ...
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6 votes
1 answer
228 views

Do we know how old the matter that makes us is?

Last weekend, I had the pleasure of visiting an observatory where there was a series of lectures to cover up the fact that there was too much cloud cover to actually observe much at all. One of these ...
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2 votes
0 answers
51 views

How the observed deuterium abundance constrains big bang nucleosynthesis?

I know deuterium can be used as a good tracer to constrain the big bang nucleosynthesis. But can anyone tell me the in details how this is actually done?
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2 votes
0 answers
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pp-Chain reactions involving $^{3}_{2}He$ - differences in S-factor

So I was looking at the pp-chain reactions that take place inside stars in a bit more detail. I got confused about the massive differences in reaction efficiencies concerning two reactions $^{3}_{2}He$...
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3 votes
1 answer
324 views

"Turn on point" for fusion?

I've read that when a body reaches about 13 times the mass of Jupiter that deuterium fusion starts and the body becomes a brown dwarf instead of a planet. I have a multiple question. Are there any ...
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1 vote
2 answers
177 views

Can you recommend a book about big bang nucleosynthesis and chemical abundances?

I am interested in learning about big bang nucleosynthesis, nuclear fusion up to iron in stellar cores and beyond iron in supernovas, and into the lithium problem (galactic abundance anomoly for ...
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2 votes
1 answer
143 views

Ionization Fraction of Helium in alternate, He dominated early universe

I'm asked to verify an expression for the ionization fraction of helium in a universe in which helium dominates baryonic matter. I'm given that the ionization fraction $X = \frac{n_{He^+}}{n_{He^+}+...
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30 votes
1 answer
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Why didn't the Big Bang produce heavier elements?

Shortly after the Big Bang, temperatures cooled from the Planck temperature. Once temperatures lowered to 116 gigakelvins, nucleosynthesis took place and helium, lithium and trace amounts of other ...
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0 votes
1 answer
334 views

How much star can star fusion fuse if star fusion can fuse hydrogen?

During stellar nucleosynthesis a star will convert a portion of its hydrogen atoms into helium. Is there a constant of how many tons of hydrogen is converted based on the mass of the star? Is it ...
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8 votes
1 answer
1k views

Why does lithium fuse at lower temperatures than hydrogen?

This is a basic question, but it's been bugging me. In the Wikipedia article for lithium burning, it states that: Stars, which by definition must achieve the high temperature (2.5 × 10^6 K) ...
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1 vote
1 answer
313 views

Is nucleosynthesis responsible for the expansion of the universe?

Is it just a coincidence that the two major expansionary periods occur close to periods of nucleosynthesis? Big Bang nucleosynthesis occurred very close to the inflationary period. Supernova and ...
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17 votes
1 answer
1k views

What would the Sun be like if nuclear reactions could not proceed via quantum tunneling?

Without quantum tunneling our Sun wouldn't be hot or massive enough to produce the energy it does at the moment. So what would have been the temperature or mass of our Sun without quantum tunneling of ...
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3 votes
1 answer
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trying to understand stellar nucleosynthesis

Trying to create a periodic table that shows "where" elements are made. For example big bang, cosmic rays, stars, supernovae etc...but reading a lot about gold,and other heavy neutron rich elements, ...
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0 votes
2 answers
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Can quantum entanglement cause nucleosynthesis to happen in stars?

Even if there isn't enough heat and energy in the star to cause nucleosynthesis, could atoms quantum entangle to create a new atomic nuclei? Or would it be quantum tunneling - if this is possible?
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8 votes
4 answers
7k views

Can we compress any object to create black Holes?

In general, when a star runs out of nuclear fuel, gravity gets the upper hand and the material in the core is compressed even further and creates black holes. I am clear till here. Now the question ...
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3 votes
2 answers
3k views

Is a star powered by fission possible?

Stars can easily fuse atoms to give of heat and radiation. But at Wikipedia it said that only sub-iron atoms give of energy when fused and take energy when split, and post-iron atoms is the exact ...
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9 votes
2 answers
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Why does iron consume more energy in the fusion process than it produces?

I understand that once a star starts fusing iron, it's doomed to collapse because iron fusion requires more energy than it releases in the process, allowing the opposing gravity of the star to cause ...
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5 votes
2 answers
148 views

Free neutrons and stellar nucleosynthesis

Both the R-process and the S-process of stellar nucleosynthesis rely on absorbing 1 (S) or more (R) neutrons. Where do they come from? I thought there are no free neutrons in stars. (Also the half-...
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11 votes
3 answers
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How can the Sun burn without oxygen?

How does the Sun burn without oxygen? It might not be burning but a big part of the society speaks of it as burning. So how does it work?
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