<p>Pretty sure from my stellar nucleosynthesis days that the p-p I chain is the dominant form of nucleosynthesis in the sun, but the p-p II, p-p III, and p-p IV chains also occur, just to a much lesser extent. Those will make Be, B, Li.</p>
<p>But, Na and Fe - and other heavier elements - mostly come from the sun not being a first-generation star: Previous supernovae formed those elements and they were incorporated into the sun, just as they were incorporated into Earth.</p>

CC BY-SA 4.0
2021-03-21T15:21:24.437Z
Be, B and Li are all destroyed in the solar interior.
ProfRob
CC BY-SA 4.0
2021-03-21T22:53:42.600Z
What ProfRob said. Yes, the various [proton-proton chains](https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain) produce deuterium, lithium, beryllium, and boron, but they all end up being converted to helium
PM 2Ring
CC BY-SA 4.0
2021-03-22T13:23:58.683Z
@PM2Ring - which means there is a small concentration of them at any given time as they are created and then further reacted.
Jon Custer
CC BY-SA 4.0
2021-03-22T14:53:29.597Z
if you're looking at minority fusion cycles in the sun and counting intermediate nucleus that are consumed in later steps: CNO is responsible for ~1.7% of the He produced (more than the p-p III branch), and produces carbon, nitrogen, and oxygen as reaction intermediates.
Dan Is Fiddling By Firelight
CC BY-SA 4.0
2021-03-22T16:39:00.907Z
@JonCuster True, but material in the core isn't visible in the Sun's spectrum, and at this stage of the Sun's life, virtually everything produced in the core stays in the core. When the Sun enters the red giant branch, there will be [dredge-up](https://en.wikipedia.org/wiki/Dredge-up).
PM 2Ring
CC BY-SA 4.0
2021-03-22T16:41:28.657Z
OTOH, a small amount of nucleosynthesis *does* occur in the Sun's outer atmosphere (and throughout the Solar System), due to [cosmic ray spallation](https://en.wikipedia.org/wiki/Cosmic_ray_spallation).
PM 2Ring
CC BY-SA 4.0
2021-03-21T05:53:51.930Z
2021-03-21T05:53:51.930Z
James K
<p>The act of fusion transfers part of atom into energy and the part left over is fused together with Hydrogen to make heavier and heavier elements.  Heavier elements create more pressure in the middle of the star which creates more and more heavier elements fusing the many nuclei together.  Once the sun starts making Iron(Fe), it dies and collapses which creates more elements.  Or explodes if a supernova and makes gold and such.  Don't know what a blackhole makes?  Maybe fuses time and matter together so it can't be separated from each other.</p>

CC BY-SA 4.0
2021-03-21T19:56:34.263Z
Our sun is not massive enough for there. It will fuse hydrogen. At a later stage it can fuse helium. After that fusion will stop in our sun. The processes you mention can happen in other -more massive suns-, but not in our sun and not at the moment. And as such do not explain why they are currently present. Both existing answers already refer to nova and other more massive suns, and they their *earlier* existance has contributed to the presence of heavier material in our sun.
Hennes
CC BY-SA 4.0
2021-03-21T22:37:02.677Z
The Sun will never make iron.
ProfRob
CC BY-SA 4.0
2021-03-23T00:19:01.480Z
Nor will it ever explode as a supernova. Once nucleosynthesis finishes, it will collapse into an extremely dense, white-hot stellar remnant, and all the gold it currently contains (which is [more than all the water in Earth's oceans](https://astronomy.stackexchange.com/questions/24590/how-much-gold-is-there-in-our-sun)) will remain trapped there forever.
Chappo Hasn't Forgotten
CC BY-SA 4.0
2021-03-21T19:28:43.137Z
2021-03-21T19:28:43.137Z
Marty
<p>The Sun is currently turning hydrogen into helium. There are no other nuclear reactions taking place at any significant rate in the Sun. The Sun will not start to make heavier elements until it reaches the tip of the red giant branch in about 7 billion years time.</p>
<p>The elements heavier than helium that are present in the Sun were almost all made inside other stars. These stars lived and died before the Sun was born 4.5 billion years ago. The nucleosynthesis products from these previous stars were recycled in stellar winds, supernovae, kilonovae and novae, and then mixed into the turbulent interstellar medium.</p>

CC BY-SA 4.0
2021-03-21T12:33:40.980Z
And of course some of that very same debris never quite collapsed into the sun and was left instead rotating around it, where it ended up... well, look at a mirror.
Euro Micelli
CC BY-SA 4.0
2021-03-22T11:59:39.573Z
I guess some minimal amount of material might also be from stars which died after the sun was born. Solar wind probably keeps the small particles at bay, but in billions of years, there will be the occasional unfortunate interstellar asteroid of younger age scoring a direct hit while passing through the system.
mlk
CC BY-SA 4.0
2021-03-22T14:50:04.810Z
[We are stardust...](https://www.google.com/search?client=safari&rls=en&q=we+are+stardust&ie=UTF-8&oe=UTF-8)
Lee Mosher
CC BY-SA 4.0
2021-03-21T08:16:08.493Z
2021-03-21T08:16:08.493Z
ProfRob
<p>I just learned that the <a href="https://en.wikipedia.org/wiki/Fraunhofer_lines" rel="noreferrer">Fraunhofer lines</a> 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 <a href="https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain" rel="noreferrer">p-p chain reactions</a> only involve hydrogen and helium? So where do these other elements came from?</p>

CC BY-SA 4.0
2021-03-21T08:03:43.277Z
See https://astronomy.stackexchange.com/questions/16311/how-can-there-be-1-000-stellar-ancestors-before-our-sun/ https://astronomy.stackexchange.com/questions/32086/origin-of-heavier-elements-on-earth/ https://physics.stackexchange.com/questions/7131/what-is-the-origin-of-elements-heavier-than-iron?r=SearchResults
ProfRob
<the-sun><spectroscopy><spectra><nucleosynthesis>
Formation of elements in the Sun other than helium
Jack the Ranger
# Formation of elements in the Sun other than helium

(Asked by: username_0 on 2021-03-21)

I just learned that the [Fraunhofer lines](https://en.wikipedia.org/wiki/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 chain reactions](https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain) only involve hydrogen and helium? So where do these other elements came from?

**Tags:** the-sun, spectroscopy, spectra, nucleosynthesis
> **Comments:**
> **username_1**: See https://astronomy.stackexchange.com/questions/16311/how-can-there-be-1-000-stellar-ancestors-before-our-sun/ https://astronomy.stackexchange.com/questions/32086/origin-of-heavier-elements-on-earth/ https://physics.stackexchange.com/questions/7131/what-is-the-origin-of-elements-heavier-than-iron?r=SearchResults  

---

## 3 answers

### Answer by username_1 on 2021-03-21. Score: 29 | Accepted answer

The Sun is currently turning hydrogen into helium. There are no other nuclear reactions taking place at any significant rate in the Sun. The Sun will not start to make heavier elements until it reaches the tip of the red giant branch in about 7 billion years time.

The elements heavier than helium that are present in the Sun were almost all made inside other stars. These stars lived and died before the Sun was born 4.5 billion years ago. The nucleosynthesis products from these previous stars were recycled in stellar winds, supernovae, kilonovae and novae, and then mixed into the turbulent interstellar medium.

> **Comments:**
> **username_9**: And of course some of that very same debris never quite collapsed into the sun and was left instead rotating around it, where it ended up... well, look at a mirror.  
> **username_10**: I guess some minimal amount of material might also be from stars which died after the sun was born. Solar wind probably keeps the small particles at bay, but in billions of years, there will be the occasional unfortunate interstellar asteroid of younger age scoring a direct hit while passing through the system.  
> **username_11**: [We are stardust...](https://www.google.com/search?client=safari&rls=en&q=we+are+stardust&ie=UTF-8&oe=UTF-8)  

---

### Answer by username_2 on 2021-03-21. Score: 3

Pretty sure from my stellar nucleosynthesis days that the p-p I chain is the dominant form of nucleosynthesis in the sun, but the p-p II, p-p III, and p-p IV chains also occur, just to a much lesser extent. Those will make Be, B, Li.

But, Na and Fe - and other heavier elements - mostly come from the sun not being a first-generation star: Previous supernovae formed those elements and they were incorporated into the sun, just as they were incorporated into Earth.

> **Comments:**
> **username_1**: Be, B and Li are all destroyed in the solar interior.  
> **username_3**: What ProfRob said. Yes, the various [proton-proton chains](https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain) produce deuterium, lithium, beryllium, and boron, but they all end up being converted to helium  
> **username_4**: @PM2Ring - which means there is a small concentration of them at any given time as they are created and then further reacted.  
> **username_5**: if you're looking at minority fusion cycles in the sun and counting intermediate nucleus that are consumed in later steps: CNO is responsible for ~1.7% of the He produced (more than the p-p III branch), and produces carbon, nitrogen, and oxygen as reaction intermediates.  
> **username_3**: @JonCuster True, but material in the core isn't visible in the Sun's spectrum, and at this stage of the Sun's life, virtually everything produced in the core stays in the core. When the Sun enters the red giant branch, there will be [dredge-up](https://en.wikipedia.org/wiki/Dredge-up).  
> **username_3**: OTOH, a small amount of nucleosynthesis *does* occur in the Sun's outer atmosphere (and throughout the Solar System), due to [cosmic ray spallation](https://en.wikipedia.org/wiki/Cosmic_ray_spallation).  

---

### Answer by username_6 on 2021-03-21. Score: -3

The act of fusion transfers part of atom into energy and the part left over is fused together with Hydrogen to make heavier and heavier elements. Heavier elements create more pressure in the middle of the star which creates more and more heavier elements fusing the many nuclei together. Once the sun starts making Iron(Fe), it dies and collapses which creates more elements. Or explodes if a supernova and makes gold and such. Don't know what a blackhole makes? Maybe fuses time and matter together so it can't be separated from each other.

> **Comments:**
> **username_7**: Our sun is not massive enough for there. It will fuse hydrogen. At a later stage it can fuse helium. After that fusion will stop in our sun. The processes you mention can happen in other -more massive suns-, but not in our sun and not at the moment. And as such do not explain why they are currently present. Both existing answers already refer to nova and other more massive suns, and they their *earlier* existance has contributed to the presence of heavier material in our sun.  
> **username_1**: The Sun will never make iron.  
> **username_8**: Nor will it ever explode as a supernova. Once nucleosynthesis finishes, it will collapse into an extremely dense, white-hot stellar remnant, and all the gold it currently contains (which is [more than all the water in Earth's oceans](https://astronomy.stackexchange.com/questions/24590/how-much-gold-is-there-in-our-sun)) will remain trapped there forever.  

---

