Did atoms in human body indeed come from stars?

  • I think I am not alone who saw videos about that we (humans) are made of same atoms which someday were in stars. In other words, some atoms in our bodies are from stars which exploded billions of years ago.



    I wonder if it is indeed true. I mean human's life begins when sperm cell fertilize egg cell. Now does that sperm cell or egg cell indeed contains some of the exact atoms from those stars?



    I know little bit strange question, but would be interesting to hear if it is indeed true, that atoms in our body are same which someday were in stars.



    In case you are wondering that's the video I am talking about: http://www.youtube.com/watch?v=9D05ej8u-gU


    As a side note on Neil deGrasse Tyson (NDT): he's a great speaker, and you might be interested in his talk for the SciCafe: http://www.youtube.com/watch?v=4KRZQQ_eICo

    I will definitely watch this, sounds very interesting.

    There's no guarantee that all the hydrogen in your body passed through a star first. Some of it may have diffused in from the Boötes void. Most of the metals, anything heavier than helium, *were* formed in stars rather than the big bang: https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis

    Technically all elementary particles are exactly the same, so...

  • stevenvh

    stevenvh Correct answer

    7 years ago

    When the first atoms came into being in the early universe they were mainly hydrogen (the smallest atoms there are) and some helium. All over the universe those atoms lumped together under gravity until the pressure and temperature became so high that the hydrogen atoms fused together to form heavier elements. The reaction is nuclear fusion, and it's the engine of all stars. First hydrogen fuses to form helium, and then in a cascade helium atoms fuse to form heavier elements.



    Many stars die as a supernova, without doubt the most violent explosions in the universe. The supernova which was just a single star becomes as bright as the complete galaxy it's part of. Remember that such a galaxy typically consists of 100 billion stars.



    During the supernova explosion all the elements from helium to the most heavy elements are thrown into space. Later they will coalesce to form planets around new stars. So indeed, everything the earth consists of comes from such an exploding star.



    And the next step is life. A single cell consists mainly of carbon, hydrogen, oxygen and nitrogen, all ultimately coming from the earth. For instance a plant will take these elements from the soil and the air, and we animals get it from plants. So the elements from the soil, which came from stars, ultimately ends up in each of our cells.


    This is so far most well explained answer, but it contradicts some other answers like Gerald's, who said that atoms in our bodies are not exact same from stars.

    @user1880405 - Gerald describes radioactive atoms, which decay to slightly different ones. In that case the atoms aren't exactly the ones which originated in stars. **But** most atoms made in stars are stable, i.e. not radioactive. But even radioactive atoms don't completely disappear to form completely new atoms; you could say that for instance they retain 90 of their 91 neutrons, while the remaining decays into a proton. All within the same atom.

    Gotcha. Now on a side note, why I asked my question in the first place, I thought maybe some of the atoms are already created in the earth in which case maybe all atoms in human are the ones which were created in earth, but not in stars.

    @user1880405 - Yes, but as I tried to explain the planets are formed from the debris of exploded stars. Larger masses form stars, and the stars attract other debris, which either is absorbed or ends up in orbits. Planets in turn attract more space stuff. We're lucky to have the giant Jupiter to be a spatial "vacuum cleaner" which attracts many meteorites and other stuff which otherwise would end up on the earth. But all in all it's all traceable to exploding stars.

    Please note that hydrogen does NOT come from stars. Almost aboslutely all of it is primigenium.

    The statement that "everything on Earth came from such an exploding star" is simply misleading and incorrect. The origins of carbon and oxygen for instance are much more complex.

    @RobJeffries - Well, feel free to tell us where the elements heavier than hydrogen and helium come from, then, if it's not from stars. You do realize that in the beginning there was only hydrogen and helium, and all that happened since is the formation and destruction of stars, do you?

    Not from "**exploding** stars". Read my answer. Roughly 50% of elements heavier than iron are made in the s-process and get into the ISM via slow stellar winds from AGB stars (for example). Much of the carbon and oxygen in the ISM gets there in the same way.

    @RobJeffries - The s-process occurs within stars, doesn't it? So the elements are created in stars. That's what I'm saying. Also, I'm not saying the supernova event *creates* the elements, it just throws them into space. You'll agree that at the time a supernova occurs it holds a *lot* of heavy elements and that a *very* high mass of it is ejected into space?

    You are still completely missing the point. About half of the heavy elements *never* come anywhere near a supernova explosion. Yes, they are created in stars, but they are not stars that end their lives in a supernova. (And BTW, supernovae explosions *do* create many of the very heavy elements through the r-process).

    Er, no. In the fusion process inside stars, there simply isn't enough pressure and heat to produce elements heavier than iron. It doesn't matter about the size of the star either. And once the star's core gets to fusing a significant amount of iron, the entire process stops. Iron itself poisons the fusion process. The only way to produce atoms heavier than iron is in a supernova. This accounts for the rarity of heavy metals in the universe, because while smaller stars shed their matter into the galaxy all the time when they die, only the rarer supernovae can produce gold, silver and uranium.

    @Ernie Er, yes. Look up s-process. You could even start on the wikipedia page, which seems to be reasonably correct. Most of the Ba, Sr, Eu, Pb (to pick a few examples heavier than Fe) are produced mainly by the s-process in AGB stars. Sure, U is made almost exclusively in supernovae as are all (the rare) elements heavier than Pb. The s-process is normally described as neutron capture, rather than fusion.

    Apologies, not Eu, that is r-process. Substitute La, or Cu or Rb.

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Content dated before 7/24/2021 11:53 AM

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