# I Chemical Elements produced inside the Sun

1. Jun 9, 2018

### DaTario

Hi All,

I would like to know if the following statement is true or false:

The nuclear processes that happen inside the Sun can produce at least one unity of each of the known chemical elements.

Best Regards,

DaTario

2. Jun 9, 2018

3. Jun 9, 2018

### phyzguy

What do you mean by "one unity"? One atom?

4. Jun 9, 2018

### stefan r

False.

Lithium and plutonium come to mind.

Assume he means one quanta. An atom. What are the odds of a 197Au atom appearing?

5. Jun 9, 2018

### DaTario

Yes, at least one atom of each of the existing elements, without any external interference. Just the Sun with its initial condition and its natural burning process.

6. Jun 9, 2018

### DaTario

Hi stefan r, thank you for the response, but why are the synthesis of Lithium and Plutonium impossible in the Sun? Please note that my question does not address the discussion about abundancies. It has to do only with the possibility of the corresponding nucleosynthesis to occur in the Sun, due to internal natural processes.

Last edited: Jun 9, 2018
7. Jun 9, 2018

### DaTario

Thank you, Chem Air, but it seems that these pages do not contain explicitly the answer, although they contain a lot of usefull information on this subject.

8. Jun 9, 2018

### rootone

A star the size of the Sun can produce Carbon,
Oxygen and Nitrogen are interesting by products of that.

9. Jun 9, 2018

### DaTario

Nothing beyond these elements? Is it impossible for an atom of iron (and others havier than iron) to appear in the Sun?

10. Jun 9, 2018

### davenn

no, nothing.

http://www.astronomynotes.com/evolutn/s7.htm

Created in and appearing in have 2 very different meanings.
you need to be very careful with your use of terms/definitions

That doesn't mean to say other elements are not present in stars the mass of our sun, but they were not created in the sun

11. Jun 9, 2018

### DaTario

I guess I understand the difference now. Appearing suggests that the element was already present in the begining of the star. Is it correct?
My question has to do with the creating part. By starting from hydrogen going step by step until the formation of , say, Uranium.

12. Jun 9, 2018

### DaTario

From this reference, I took the following:
"The atoms heavier than helium up to the iron and nickel atoms were made in the cores of stars (the process that creates iron also creates a smaller amount of nickel too). The lowest mass stars can only synthesize helium. Stars around the mass of our Sun can synthesize helium, carbon, and oxygen. Massive stars (M* > 8 solar masses) can synthesize helium, carbon, oxygen, neon, magnesium, silicon, sulfur, argon, calcium, titanium, chromium, and iron (and nickel). Elements heavier than iron are made in supernova explosions from the rapid combination of the abundant neutrons with heavy nuclei. Massive red giants are also able to make small amounts of elements heavier than iron (up to mercury and lead) through a slower combination of neutrons with heavy nuclei, but supernova probably generate the majority of elements heavier than iron and nickel (and certainly those heavier than lead up to uranium). The synthesized elements are dispersed into the interstellar medium during the planetary nebula or supernova stage (with supernova being the best way to distribute the heavy elements far and wide). These elements will be later incorporated into giant molecular clouds and eventually become part of future stars and planets (and life forms?)"

A small part of my question is still standing on its foot. When this author, Nick Strobel, says that Stars around the mass of our Sun can synthesize helium, carbon, and oxygen. is he meaning that we are not to expect relevant amount of other heavier atoms to be produced (by nuclear processes) in the Sun or that we must accept that the Sun has not sufficient energy to produce even one atom of those heavier elements, like iron or uranium, for instance?

13. Jun 10, 2018

### davenn

Yes, they have come from other massive star supernovas and were present in the dust/gas clouds that coalesced into the sun and the planets

Yes, there isn't enough energy for reactions to produce those heavier elements. It takes more massive stars than our sun

Even one atom of ??
I doubt anyone could prove or disprove that and the big scheme of things, it's hardly relevant
I would rather say … detectable amounts that were guaranteed to have been CREATED in the Sun

Last edited: Jun 10, 2018
14. Jun 10, 2018

### DaTario

Thank you, davenn. Let me just present a last idea on this discussion, which is to me a bit confusing. When we study the thermal state, we learn that, at a given temperature, the probability of existence of particle with a very very high velocity is not zero, although it is very small. With this in view, must we say that the nuclear process that produces a heavier element (just one atom of it) in the Sun is, in fact, impossible?

(This ideia of thermodynamics leads me to think that it is only very unlikely to occur, but once in a while it happens, yielding a negligible population of these species.)

15. Jun 10, 2018

### davenn

That's OK for things outside the core of a star.
You do know that it takes 1000's of years for photons produced in the core to get to the surface of the sun ?
there's no room for very high velocities in the core of a star.... the densities are too high

16. Jun 10, 2018

### Bandersnatch

I think there is always a non-zero cross section for any fusion reaction to occur, at any temperature above zero. That is to say, there is no hard cut-off absolutely preventing further steps from happening (unless there is? Let's ask @mfb ).
So the probability of there occurring the entire chain of reactions even up to uranium fusion should also have a non-zero probability.

The question would then become 'how probable is it that a star like the Sun can produce at least one of all elements, up to uranium (or even heavier), over its life time?'.
The answer would require running some actual numbers, which I don't have. My gut feeling, though, is that it'd be as probable as for a bowl of petunias to suddenly appear in Earth's orbit.

17. Jun 10, 2018

### Staff: Mentor

Lithium is created routinely and in huge amounts in one of the proton-proton fusion chains (P-P II).
A couple of uranium atoms will capture neutrons and become plutonium. That is not a common process, but the Sun consists of 1057 nuclei.
The density doesn't matter as long as the system is not degenerate (it is not).

You can multiply the Gamow factor with the Maxwell-Boltzmann distribution to get a rough estimate of the probability that particles have enough energy and fuse. For two protons this chance is very small, but with the huge number of collisions it still happens once in a while. Try the same for two helium nuclei, or even heavier nuclei.

Who said it has to be fusion? Our Sun contains uranium, uranium can fission spontaneously; it releases a few neutrons in the process. The neutrons can be captured by all other elements in the Sun, often allowing them to beta decay to a different element. This is not a common process, but we have 1057 nuclei to work with - it does happen.
In addition, cosmic rays strike the surface, leading to various reactions.

Superheavy elements would need some really weird production mechanism, however - a heavy ion coming from space hitting a heavy ion in the outer regions of the Sun or something like that. I'm not sure how often that happens. Probably more than once per 5 billion years.

18. Jun 10, 2018

### stefan r

There is a chance that a bowl of petunias will appear in Earth's orbit. The probability of a quantum tunneling event is strongly effected by the number of particles involved and the distance that each particle moves. The atoms in your foot rearranging into a bowl of petunias at the end of your leg is much more probable than a bowl of petunias appearing in orbit unless it happens in a satellite because the particles need to move a shorter distance. The core of the sun has high density so the petunia probability should be higher. It is safe to say that a spontaneous quantum bowl of petunias is so unlikely that it has never occurred anywhere in the visible universe since the big bang.

I saw the calculations for one mole of water tunneling in a text book. The author gave estimates for tunneling from one shot glass to an adjacent shot glass as water. That is less likely than tunneling out of the shot glass. That was much less likely than tunneling event inside the shot glass where the atoms in the water molecules move a few angstroms and become iron and release enough energy to destroy the neighborhood. Even though a spontaneous nuclear explosion in your toe is much much more likely it is still highly unlikely that is has happened anywhere in the visible universe within 4 x 1017 seconds.

If the same mechanism can happen on Earth or Ceres then I think it is reasonable to say it is not part of "the nuclear processes in the Sun".

The core of the sun burns lithium faster than it produces lithium.

I would not include cosmic ray spallation or spontaneous fission. Both can occur on Earth.

7Li is in the p-p chain. 6Li can be formed by 3H and 3He. 3H should be extremely rare. Is there an easier route to 6Li?

19. Jun 10, 2018

### Staff: Mentor

OP was talking about a single atom and the Sun. One isotope of lithium is enough and what happens on Earth is not relevant.

D + He-4 doesn’t have enough energy I guess (and photon emission - rare process if possible at all)? Can’t check right now.

20. Jun 10, 2018

### Bystander

Along that same/similar line of inquiry, thirty to forty years ago, 8Be was "forbidden"/had an infinitessimal lifetime; any more recent measurements/results?

21. Jun 10, 2018

### Staff: Mentor

Its lifetime is still very short, $(6.7\pm1.7)\cdot 10^{-17} s$.

Edit: Minus sign

Last edited: Jun 11, 2018
22. Jun 10, 2018

### Bystander

Minus? Thanks.

23. Jun 10, 2018

### alantheastronomer

The nuclear burning cores of sun-like stars are convective, which means they have a uniform temperature. While it's true that energies of an isotropic medium lie along a gaussian curve, with few atoms along the high end of the curve, their energies are insufficient to produce the high atomic mass elements to which you are referring.

24. Jun 11, 2018

### DaTario

But the question posed in the OP is relative to the possibility of creation of these elements by any natural process inside the Sun; it is not related to the corresponding lifetime.

I would like to ask if you (alantheastronomer) agree with the following sentence, which is your sentence, quoted above, with a small change (bold):

The nuclear burning cores of sun-like stars are convective, which means they have a uniform temperature. While it's true that energies of an isotropic medium lie along a gaussian curve, with few atoms along the high end of the curve, their energies are insufficient to produce even just one of the high atomic mass elements to which you are referring.

25. Jun 11, 2018

### stefan r

I think G and F stars do not have convective cores. convection is outside of the tachocline. Many K dwarfs are convective to the core. Types A,B,O have core convection.