Origin of the Elements in the Solar System

“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.” — Carl Sagan

This is an evocative statement. It gets at the heart of the matter. However, it leaves out all the different ways that stars make the elements. It is not just collapsing stars, it is merging stars, burping stars, exploding stars, and the start of the Universe itself.

Below is the latest version of an evolving periodic table color-coded by the origin of the elements in the Solar System. An original version of this was made by Inese Ivans and me in 2008 and refined and improved by Anna Frebel. Versions highlighting different aspects of the physical processes are available on Inese Ivans’ website.

My current version of the periodic table, color-coded by the source of the element in the solar system.

My current version of the periodic table, color-coded by the source of the element in the solar system. Elements with more than one source have the approximate amount due to each process indicated by the amount of area. Tc, Pm, and the elements beyond U do not have long-lived or stable isotopes. I have ignored the elements beyond U in this plot, but not including Tc and Pm looked weird, so I have included them in grey.

For this version, I tried to avoid the technical terms and jargon used in the original plot. I also updated the sources of the heavy elements to reflect the current semi-consensus. This graphic draws on an enormous amount of labor from astronomers and physicists. In an upcoming blog post, I will give details on my sources and assumptions for interested parties. Note that this is for the solar system. There will be additional versions showing what this plot would look like if you were in the early Universe, or if you consider the origin of the elements on the Earth, etc.

However, the main point of this blog post is to present the chart and address the following question:

Why does your version have different information than the well-known Wikipedia entry?

Nucleosynthesis periodic table

Wikipedia version, based on the original from Northern Arizona Meteorite Laboratory.

Here is a discussion of the some of the differences between the Wikipedia version and mine. In many cases, the Wikipedia graphic is presenting information that is flat-out wrong. I am trying to avoid going into all details in this single blog post. The underlined phrases below represent possible topics for future blog posts where I (or colleagues I coerce bribe ask) can go into more in more detail later, including why we think we are on the right track.

  • I will assume that “Large Stars” and “Small Stars” are “High-Mass Stars” and “Low-Mass Stars”, respectively. It does not make sense to think of nucleosynthesis origin having to do with the radius of the stars. As this wonderful graphic from NASA’s Chandra website shows, all stars at the end of their lives swell up to red giant and supergiant stars. In its death throes, a low-mass star can have a much larger radius than a normal high-mass star. Note that the original source cited by the Wikipedia article just has the chart, with no additional information or links that I can find.
  • High-mass stars end their lives (at least some of the time) as core-collapse supernovae. Low-mass stars usually end their lives as white dwarfs. But sometimes white dwarfs that are in binary systems with another star get enough mass from the companion to become unstable and explode as so-called Type-Ia supernovae. Which “supernova” is being referred to in the Wikipedia graphic is not clear. The interpretation that makes the graphic the least wrong is the “supernova” here means “Type Ia Supernovae” or “exploding white dwarfs” as I call them. I will assume that “Large Stars” refers to the production in high-mass stars both during their lives and during the explosion that spews products of their nuclear fusion into the interstellar gas. It would also be possible to think that “Supernovae” refers to both massive star core-collapse supernovae and exploding white dwarfs. In this case, “Large Stars” could mean that massive stars make it before they explode and the supernovae is just the mechanism for kicking out. These categories are therefore 1) confusing and 2) incorrect no matter how you slice it.
  • Dying low-mass stars (aka “Small Stars”) make substantial amounts of the heavy elements, including most of the Pb in the solar system. There should be a lot of yellow in the bottom half of the diagram. I don’t agree that Cr and Mn are made only in “Large Stars”, but Fe is made in both “Large Stars” and “Supernovae”. Basically all the iron in the Universe is made in explosive nucleosynthesis. The iron that massive stars make right before they explode as supernova is all destroyed/collapsed in the remnant. And so on.
  • The information for Li is incorrect. 6Li is indeed made by cosmic rays (fast-moving nuclei) hitting other nuclei and breaking them apart. But most of the far more common 7Li isotope is without question made in low-mass stars and spewed out out into the Universe as the star dies. Some 7Li is also made in the Big Bang and a small fraction by cosmic ray fission.
  • This post does not need to be any longer, but I would like to end by pointing out a difference between the Wikipedia graphic and my graphic caused by the fact that we still don’t know everything. A fraction of the heavy elements, including most of the Au, are formed in the “rapid neutron-capture process“. Where that happens is currently in dispute. It could be in massive star supernovae close to the forming neutron-star. More recently, there is compelling evidence that most of the r-process happens when two neutron stars spiral together and merge. That is why “merging neutron stars” is a category in my chart, but “Supernovae” takes the role in the Wikipedia chart.

Note

Backing this statement up with actual evidence may be the basis for a future blog post. Please let me know in comments if you are interested in a blog post on a particular subject.


The Source of it all

Here is the original version, done with markers:

This is what happens when you give two astronomers who are tired of reminding everyone about which elements go with which process a periodic table, a set of markers, and time when they should have been listening to talks. A heartful thanks to Inese Ivans for coming up with this idea.

This is what happens when you give two astronomers who are tired of reminding everyone about which elements go with which process a periodic table, a set of markers, and time when they should have been listening to talks. A heartful thanks to Inese Ivans for coming up with this idea.

10 thoughts on “Origin of the Elements in the Solar System

  1. Pingback: La tabla de los elementos según su origen en el universo | obiKuo

    • Thanks for the link. A quick correction: SDSS is not funded by NASA. We are mostly funded by our member institutions, with some contribution from the US Department of Energy.

  2. Very nice, very good work.
    I’ll ask you to also add the short-lived isotopes. I think it’s interesting where they are formed despite being impractical, and for completion issues.
    I am also very curious about the source of heavy elements. For example, are Np and Pu missing on the wild because they’ve already fizzed away or have they been never created on nature?

    Thanks a lot.

    • Thanks for the comment. I will put “discuss the formation of the short-lived (including trans-U elements)” on my blog to-do list.

  3. Really excellent work! I love it! This is so much more accurate and informative than the current version on Wikipedia, which is just plain painful to look at. I’ve wanted to correct that figure every time I looked at it, so thank you for actually doing it. 🙂

    I understand your reasoning for using NS mergers, but that suggests that supernovae (II) don’t play a significant role for the neutron-rich elements. I wonder if it would be worth replacing that with simply “r-process”, considering the current debate about the site, although I agree that at least at high metallicities the arguments for the NS mergers are becoming rather compelling. But maybe r-process will be too technical? On the other hand, labeling those elements “r-process” would underline that we don’t actually know the site yet, which I would consider an important point, that you also highlight above. Then people are free to go look up the r-process and check out the different candidates.

    I dunno about Pm, but I think Tc should be put in the “dying low-mass stars” category, even if it’s unstable. It is both produced and observed in AGB stars, so even though it is not a stable element, we know the production site. But I suppose the distinction between “origin of the elements” and “origin of the elements in the Solar System” is fairly crucial here. 🙂

    I’d love to see a blog post discussing the different potential r-process sites btw.(neutron star mergers, type II supernovae, MHD jets, … ?)

    Thanks for doing this work once again, it’s great!

    • Hi Anders! I agree that the vermilion color would most correctly be labeled “r-process”. But that’s not so helpful to people who are not us & that was my main goal. However, will make a revised version with “merging neutron stars?”. Hooray for question mark! Would you like to write a guest post about the r-process and the current debate on its site for this blog. I would love to have other experts chime in here.
      I look forward to making a truly revised version when we know where the site of the &%#()$@^ r-process is.

    • Yes, good point. I will chat with Inese and see why we disagree. I think I am correct (obviously), but could learn something!

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