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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:

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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: –  stevenvh Feb 17 '14 at 12:12
I will definitely watch this, sounds very interesting. –  user1880405 Feb 17 '14 at 12:19
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: –  Wayfaring Stranger Aug 14 at 13:39

6 Answers 6

up vote 8 down vote accepted

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.

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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 Feb 17 '14 at 11:53
@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. –  stevenvh Feb 17 '14 at 11:59
Please note that hydrogen does NOT come from stars. Almost aboslutely all of it is primigenium. –  Envite Feb 18 '14 at 8:25
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. –  Rob Jeffries Apr 27 at 5:59
@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? –  stevenvh Apr 28 at 8:29

I might not be that much conceptual to you, but do you believe that stars are made up of Hydrogen (and Helium too). Hydrogen is a part of all the organic compounds. We humans are made up of billions of organic compounds, which in turn do contain Carbon, Hydrogen and Oxygen as their basic element and other compounds such as Sulphur, Phosphorus and other fats. And I guess a biology student would tell you more clearly what a sperm contains and what and how do these elements ressembles to those who are in Stars.

When a star collapses, it liberates out elements such as Carbon, Iron etc. Which maybe you're talking about. So that sperm consists of the same elements that the Star had at the time of its death (well not death you might know a better word for the star's ending period).

However, this doesn't make sense that these atoms are really the exact same or the actuall ones that were in the Stars many years ago. No such theory has been provided.

What does Star contain and what it liberates:

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Thanks Afzaal. I of course understand that the same elements which are in human body were in stars, but my question indeed is, are there same exact atoms in our bodies from the stars, because it seems like that's what the video tries to say. –  user1880405 Feb 17 '14 at 10:17
@AfzaalAhmadZeeshan You are wrong. The body does NOT made up any elements. Making elements are nuclear reactions, and we do not do that in our bodies, only chemical reactions that do not change atoms, just combine them. –  Envite Feb 17 '14 at 10:57
Ha ha ha @envite what are you? An alien? Everyone knows that the body is made up of elements. And nuclear reactions are used to generate energy not elements. Elements are formed as a by-product. –  Afzaal Ahmad Zeeshan Feb 17 '14 at 11:23
@AfzaalAhmadZeeshan No sorry, Envite is correct: Our body is able to change molecules, not chemical elements. –  Gerald Feb 17 '14 at 11:32
@AfzaalAhmadZeeshan you said (cite) "These elements are made up in our body" and that is wrong. Then you said "the body is made up of elements" which is true. Please do not confuse one thing with the other. –  Envite Feb 17 '14 at 12:37

Think about it this way, there are two options about how life began on earth: abiogenesis(life began on earth) and panspermia (life began somewhere else and from something like a meteor strike it continued to evolve on earth),at least those are the ones the are more dominant than other theories. Either way if life began to evolve on earth from matter that was on earth than it is suitable that whatever life evolved here would contain the same materials as earth, and earth originated from other starts, dust and debris that was around 4.5 billion years ago same thing for the second theory I mentioned. So I would suggest reading more on abiogenesis and panspermia it may satisfy your curiousity and answer your question.

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Thanks, I understand what you are saying, but I am asking a question: are some of the atoms in our bodies are exact same which someday were stars? That's all I ask and there is either "yes" or "no" answer to it. P.S. in no way I am trying to be rude. –  user1880405 Feb 17 '14 at 10:57

Your body has hydrogen and heavier elements.

Most hydrogen in your body (really most of it) is primitive hydrogen from the origins of the Universe. Same would happen for Helium but we don't have it (almost none) on our bodies.

For all other elements, yes, they come (really most of them) from a star.

Sequence is approximately as follows:

When the Universe was young, our Galaxy was young: it was a cloud made of Hydrogen and Helium. Then, some stars (called Population III stars) were born and started burning hydrogen into helium, and on the latter stages of their lives they burned up helium into weighter elements like carbon, nitrogen, up to very small amounts of iron (the most stable element), and beyond that up to uranium.

Depending on their mass, of course. The smaller of these stars may be still around us, and the bigger ones exploded, sending these new elements to the galactic (a.k.a. interstellar) medium.

Then, from the now enriched medium, new stars were born (called Pupulation II stars). These ones had of course a lot of hydrogen and helium, but they had also some of the heavier elements. In turn, some of them are still observable (smaller ones, which last longer) and some of them exploded (bigger ones, which burn faster).

This second wave of stellar explosions enriched more the interstellar medium (gallactic medium) so a new generation of stars could be born. These are known as Pupullation I stars. Our Sun is one of them.

But not all the mass of the cloud which formed our Sun went into the Sun. Some if it made up the planets, and thus, ourselves.

So the atoms on our bodies come from the pre-planetary cloud, which consisted in original hydrogen enriched by Popullation III and Popullation II explosions.

Please note: due to chemical reactions, electrons in the atoms do not need to be the same they were while they were ejected by the stars, but the nucleus are.

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Thanks for a detailed answer. But I still didn't read answer to my question: are some of the atoms in our bodies are exact same which someday were stars? (Key word is "exact") –  user1880405 Feb 17 '14 at 11:07
Answer for "exact" is "Most probably no" because all atoms in our bodies are involved in some molecule, which imples electron changes. If the question were about exact nucleus it would have been "Yes for most of them". –  Envite Feb 17 '14 at 12:39
This answer is misleading. It claims that all the heavy chemical elements are made in massive stars that explode. –  Rob Jeffries Apr 27 at 6:05
@RobJeffries where else do you think heavy elements can come from? –  Envite Aug 14 at 12:08
@Envite Start your research with the s-process. AGB stars are heavy element factories that do not explode. In fact, why not read my answer. –  Rob Jeffries Aug 14 at 13:07

Almost all hydrogen nuclei (protons), some helium atomic nuclei and traces of lithium nuclei are thought to have formed early in the universe, after the big bang. Almost all other atomic nuclei are thought to have formed in stars or have decayed from atomic nuclei, which have formed in stars. A minor fraction forms by high-energy collisions with cosmic rays.

The electrons of the hull of atoms in parts formed during the big bang, part of them come into existence, when neutrons decay to protons. These neutrons may have been free neutrons, or neutrons bound in instable atomic nuclei.

Hence our body doesn't contain the exact same atoms as they formed in stars. But without stars most of the atoms besides hydrogen in our body wouldn't exist.

Our body contains many of the exact same atomic nuclei, as they formed in stars, not the exact same atoms/ions.

To be a little more precise: Our body doesn't contain many free atoms, but mainly molecules and ions.

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The chemical elements in our bodies are inherited from the Earth. The Earth was formed in a disc of gas and dust swirling around the protosun 4.5 billion years ago. The material that formed the Earth was a selection of the material from that protostellar nebula that was itself once part of a larger molecular cloud.

So the atoms in our body were once part of this molecular cloud, so we need to understand how they got there.

After the first ten minutes or so, the universe contained mainly hydrogen, helium and some traces of lithium, deuterium and tritium - and that's all. No oxygen, iron, carbon etc.

Almost all of the heavier chemical elements are made inside stars. We could stop there - the atoms of carbon, oxygen, calcium etc. in our bodies must have been made in stars, and since these atoms/nuclei are stable, they must survive unchanged (you could argue about whether their electrons get swapped about in chemical reactions etc., but since electrons are indistinguishable this hardly matters).

But how do they get into a molecular cloud and what sort of stars make these elements? A couple of answers correctly identify massive stars that explode as supernovae as important. But they are by no means the only contributor, or even the most important contributor for some elements.

If we take carbon and nitrogen, these are manufactured in nuclear reactions inside stars of even a bit less than a solar mass during the horizontal branch and asymptotic giant branch stages. These stars may be less massive and produce less C and N than massive stars, but there are many more of them. The central material is mixed to the surface during thermal pulses and the outer envelope, enriched in a variety of chemical elements, is gradually lost into space via a slow wind. This is a major source of carbon, nitrogen, fluorine, lithium and a number of heavy elements - Ba, La, Zr, Sr, Pb and many others - produced in the s-process. About 50% of the elements heavier than iron are made in the s-process, which can occur in both massive stars that explode (mainly isotopes with $A<90$) and the less massive AGB stars with slow, massive winds (elements up to lead and bismuth).

Iron, nickel and many other elements such as sulphur and silicon are also produced during type Ia supernovae. This is the detonation of a white dwarf, the end stage of a low-mass star, after mass transfer or merger. Milder novae explosions caused by the ignition of material accreted onto a white dwarf also enrich the interstellar medium.

All these different processes produce distinctive patterns of element abundances.

The enriched material is swept up by neighbouring supernova explosions, by interactions with spiral arms and other molecular clouds. It cools, condenses and collapses to form a new generation of stars.

Analysis of "presolar grains" found inside meteorites tells us what our solar system formed from. These analyses tell us that all of the above processes were important in making the chemical elements that made up the Earth and hence those in our bodies.

[Further details on the production of elements heavier than iron (including supernovae, low-mass AGB stars, colliding neutron stars etc.) can be found in my Physics SE answer to this question. ]

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