Questions tagged [nucleosynthesis]
Questions to do with how new atomic nuclei are created inside the universe.
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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 ...
28
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1answer
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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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0answers
21 views
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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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 ...
9
votes
1answer
158 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 ...
27
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2answers
4k views
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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2answers
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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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1answer
141 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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0answers
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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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0answers
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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 $^{3}_{2}He$...
3
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1answer
186 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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2answers
95 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 ...
2
votes
1answer
101 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^+}+...
29
votes
1answer
5k views
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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1answer
260 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 ...
7
votes
1answer
910 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) ...
0
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1answer
216 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 ...
14
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1answer
900 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 ...
3
votes
1answer
309 views
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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2answers
155 views
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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4answers
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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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2answers
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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 ...
7
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2answers
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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 ...
3
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2answers
103 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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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?
