Lawrence M. Krauss states "Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand."

For Earthlings, is this most probably correct? We know we are the dust of at least a first generation star, but isn't it possible that all our material came from the extinction of a single first generation star, especially given how early in the universe's lifespan we find ourselves? Is there any evidence or argument to support Krauss' claim?


3 Answers 3


The statement by Krauss is highly inaccurate.

"Every atom in your body came from a star that exploded". No. Most of the hydrogen in your body came from the big bang. A large fraction of the carbon, some of the nitrogen and lots of the elements heavier than iron were made in intermediate mass stars that never exploded as supernovae.

"the atoms in your left hand probably came from a different star than your right hand." This implies that you are made up from the debris of only a few previous stars. This is a false picture. The Sun is the product of (at least) millions of previous stars. Stars more massive than the Sun have short lifetimes compared with the Galaxy. They live their lives and scatter their products into the interstellar medium, where it is mixed on timescales that are also much shorter than the Galactic lifetime. The Sun (and therefore you) will contain nuclei from a large fraction of the $\sim 10^9$ stars that lived and died in our Galaxy before the Sun was born.

The details are in the linked questions, but also see Origin of elements heavier than Iron (Fe) and https://astronomy.stackexchange.com/questions/16311/how-can-there-be-1-000-stellar-ancestors-before-our-sun/16313#16313


There is no definite answer to this question. Krauss knows the field far better than I do, but I would imagine he was simply stressing the general make up of proto stellar clumps, composed of elements from many stellar explosions.

Sure, we could have obtained all our elements from one star, in fact I asked a question Formation of Solar System, a while back on whether we knew what star it was that exploded and compressed the gas cloud that comprised the early Solar System.

But what probably caused Krauss's comment was the fact that proto-stellar clouds are absolutely enormous, needing the material from many stars, so the odds are that he is correct and it is likely that we are here now because of the debris of more than one particular star.

Please note there is a much fuller related answer to this question at Recyled Stellar Material .

  • $\begingroup$ Could you please link your former question on which star gave rise to our dust? $\endgroup$ Oct 8, 2016 at 2:20
  • $\begingroup$ Thank you. I read your other post and it is interesting the shock wave curves in the presence of the cloud. It reminds me of how they use a mix of high and low speed explosives to implode nuclear weapons. $\endgroup$ Oct 9, 2016 at 12:30
  • $\begingroup$ Hi Paul, there are plenty of articles regarding the dust/gas clouds and they all seem to stress two things: the extremely low density of the "cloud" and the fact that, as you say, they need a solid kick from what's basically related to a shaped charge, to get gravity involved as the particles get closer. Apologies if you have already read this, but the links off of it are interesting :en.wikipedia.org/wiki/Star_formation $\endgroup$
    – user108787
    Oct 9, 2016 at 12:41
  • $\begingroup$ "Sure, we could have obtained all our elements from one star,", no we couldn't and it is an empirically established fact (from the mixture of isotopic compositions in pre-solar grains found in meteorites) that we are not. $\endgroup$
    – ProfRob
    Jan 25, 2019 at 10:18

Most definitely more than one dying star. Think firstly about how the solar nebula collapsed nearly 10 Gyr after the Big Bang.

The most massive stars have lifetimes of a few million years at most, producing nearly all elements up to Fe and a good number beyond from the r-process, and s-process to much lesser degree. Hundreds of millions of these stars cross-pollinated the Milky Way over billions of years and would eventually contribute to the solar nebula. Stars that are less massive, ones that become AGB stars are the majority of s-process environments in the universe. Stars up to 10 solar masses reach the AGB branch, meaning that lifetimes of these stars can be as low as several-dozen million years. This probably means that millions of these stars contributed to the solar nebula as well.

This doesn't even consider all of the nuclei created by stellar remnants such as Type Ia supernovae and neutron star mergers and other processes.

When you hear that statement the atoms in your left hand came from a different star from the ones in your right hand, it's more realistic to say that nearly every non H and He atom in your body most likely all came from different stars.


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