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Professor Oliver Manuel, a professor of nuclear chemistry at the University of Missouri-Rolla, claims in the article Sun Is Made Of Iron, Not Hydrogen, Professor Says that

iron, not hydrogen, is the sun's most abundant element.

Specifically, he and his colleagues postulate that

"We think that the solar system came from a single star, and the sun formed on a collapsed supernova core," Manuel says. "The inner planets are made mostly of matter produced in the inner part of that star, and the outer planets of material form the outer layers of that star."

Is there evidence to support or refute Professor Manuel's theories?

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  • $\begingroup$ Perhaps, the Earth's age is a reliable proof against their theory: 4billion years could be enough time to dissipate residual heat. We could compare this with White Dwarfs models, and account for an iron core. $\endgroup$ – Py-ser Oct 6 '14 at 10:14
  • $\begingroup$ That was pretty much my point regarding iron being the final product of currently understood stellar fusion processes. If fusion had stopped, four billion years is a long time for it to be still as hot as it is. $\endgroup$ – Dikran Marsupial Oct 6 '14 at 11:41
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    $\begingroup$ The claims don't seem to refute the current model. It seems rather unlikely that a sun could form from the remains of a star that already died. Regardless, if he's looking for support he needs to find evidence that actually refutes the current model. $\endgroup$ – Mitch Goshorn Oct 6 '14 at 19:05
  • $\begingroup$ Right, I misused the word: I meant, they gave a new interpretation. $\endgroup$ – Py-ser Oct 7 '14 at 6:34
  • $\begingroup$ Scientists thought something similar to what is proposed here in regards to the composition of the sun, until Cecilia Payne, in what has been called the "most brilliant PhD thesis ever written in astronomy" showed that the sun is made mostly of hydrogen. $\endgroup$ – NeutronStar Nov 20 '14 at 3:36
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If the sun was principally composed of Iron, then this would be apparent in the spectrum of light from the sun (which is how we know what stars are made of) (but see comment by @Keith Thompson below, the spectra only tells you about the surface, rather than the core). The fact that all solar physicists bar one seem to think it is made up of hydrogen and helium strongly suggests this is not the case.

If the sun were made of iron, then I suspect that would require a revision of our understanding of nuclear fusion, as iron is the product of the final fusion reaction that stars can support, unless of course the theory is that the sun is no longer undergoing fusion reactions and all we have been seeing for the last 4 billion years+ is the residual heat of the core.

Apparently heliosiesmology suggests there isn't that much iron in the suns core (although the physics is beyond me, so caveat lector).

As a further point, if the sun is primarily made of iron, it becomes difficult to explain why the planets (especially the gas giants) have so little of it. It is reasonably straightforward to explain why the inner planets have lost much of their original hydrogen and helium, but rather more difficult to explain how the outer planets could have become hydrogen enriched.

Update. Dr Manuel's website claims that "About 99% of the sun has the same composition as ordinary meteorites.". The density of carbonaceous chondrite meteorites is about 2100-34700 kg/m3 (with porosity being an issue). The mean density of the sun is 1410 kg/m3. Given the temperature and pressure within the suns' core, if it had a similar composition to a meteorite its' porosity would be zero, and hence even more dense than an ordinary meteorite. There is a problem with accounting here, if 99% of the sun had a composition similar to that of a meteorite, it would have to be full of voids to have the suns observed density. The figures just don't add up as far as I can see (although how materials may behave at ultra high temperatures and pressures means intuition may be invalid here).

For Manuel to be right, pretty much all we know about stars must be wrong.

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    $\begingroup$ @Py-ser I am no expert on this (read a couple of books on planetary science, but that is about it), my main aim in answering the question was to point to a forum more likely to have a definitive answer (while giving a couple of lines of evidence that make me highly doubtful). However if a new model requires the overturning of what we know about nuclear fusion in stars, it becomes a very big claim, and therefore requires very big evidence. $\endgroup$ – Dikran Marsupial Oct 6 '14 at 11:37
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    $\begingroup$ As an aside, if you look up Prof. Manuel's articles on google scholar, they have been very sparingly cited and the person that cites them most regularly is Prof. Manuel himself. Science is generally pretty open to people publishing unlikely ideas, but the usual consequence when the evidence provided is inadequate is that they are ignored. That seems to be the case here. I suspect the idea is not impossible, but it requires too many large adjustments to other areas of physics to work, and hence isn't considered plausible by the research community. $\endgroup$ – Dikran Marsupial Oct 6 '14 at 11:52
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    $\begingroup$ The Sun's spectrum only tells us about the composition of the visible surface. Hypothetically, if the core were mostly iron and the surface were mostly hydrogen and helium, that would be consistent with the spectrum we see. I don't take the "Iron Sun Hypothesis" at all seriously, but the spectrum isn't what refutes it. $\endgroup$ – Keith Thompson Oct 6 '14 at 16:08
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    $\begingroup$ I would have thought that an iron core would be significantly more dense than a core of metalic hydrogen. The density of the sun can be measured by its diameter and its mass deduced from its gravitational effects. I would have thought that an iron core would put severe constraints on the composition of the sun's outer layers. I doubt anybody has done the calculations though as nobody seems that interested in Manuel's theory. I'd be very interested if anyone here can comment on this (I'm a statistician not an astronomer/astrophysicist!) $\endgroup$ – Dikran Marsupial Oct 6 '14 at 17:48
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    $\begingroup$ @Py-ser perhaps you would like to explain why some of the other answers are wrong, as Keith did, rather than just state it. Or better still, write an answer of your own, that is the point of Stack Exchange sites. $\endgroup$ – Dikran Marsupial Oct 7 '14 at 9:43
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Even if the answer has already been accepted, more evidences can contribute to this thought-provoking topic.

I think, as it has been mentioned, eliosismology is a good way to map the interior of the star, but I am not able to argue about it.

Another disproof, comes from neutrinos. Interior of Sun can be investigated by neutrinos detection, which do not interact passing by the outer shells, and can directly say where they come from, and how. Standard solar theory predict neutrinos production by p-p chain. This has been observed, even if the neutrino flux is about $1/3$ than the expected one, because of the neutrino oscillation. Now, this theory become solid after Bruno Pontecorvo, but I do not think we have any other evidence of observed neutrino oscillation.

Furthermore, Earth's age is helping us. We know Earth is ${\sim}4$ billion years old, that is roughly the age of the Solar System and the Sun itself. From Niels Brendt website, we know that after such a long time, the white dwarf luminosity has become much fainter then Solar (where Solar is referred not only to the Sun, but to general G2 main sequence stars). Neutron stars cool even faster. And this is obviously not observed: if Manuel's conjecture was real, Sun should be much fainter now. To this, add that they say that their supposed SN happened something like 5 billion years ago...

As a final note, I would highlight that, not only this author has never been mentioned in literature, that is (as we know) synonym of poor quality, but he actually never published (at least since 10years or so) in any refereed paper, which is automatically translated, to me and I think to the community, as not science.

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  • $\begingroup$ +1 for neutrino argument, I will look that up in more detail. Dr Manuel has published in a variety of journals and conference proceedings, the lack of citations is more an indication that the research community don't find his arguments compelling (or perhaps simply wrong), rather than not being science. Whether something is science doesn't depend on whether it is right or wrong, or even plausible. Popperians would say it just needs to be falsifiable, which Manuel's theory clearly is. Most scientists end up about as well cited as Manuel appears to be, it isn't unusual. $\endgroup$ – Dikran Marsupial Oct 9 '14 at 9:15
  • $\begingroup$ @DikranMarsupial, I mean, from a quick reasearch I didn't find any usual refereed astrophysics journals where Prof. Manuel published, like A&A or ApJ. My opinion is that, if your work does not pass through a referee critic analysis, probably it is not scientifically correct. $\endgroup$ – Py-ser Oct 9 '14 at 15:05
  • $\begingroup$ My point was that "not scientifically correct" is not the same thing as "not science". I would venture that the majority of papers that do get past peer review are either wrong or misguided or not useful. There are plenty of papers out there with several hundred citations where the method doesn't actually work on non-trivial problems (I know this as I tried replicating one this week). Peer review is at best a basic sanity check, and it regularly fails in both directions. Best not to be unduly harsh on the authors concerned. $\endgroup$ – Dikran Marsupial Oct 9 '14 at 16:04
  • $\begingroup$ @DikranMarsupial, yes, I agree that peer reviewing does not guarantee quality 100%, that is why, if you do not even pass that, it is just a game. In the end, science or not can not be a matter of opinion. But this, again, is my biased and not-much-experienced thought. $\endgroup$ – Py-ser Oct 10 '14 at 1:23
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I think Mr. Marsupial's answer should get a star, but to put some of this in layman's terms, here's my answer.

The process of fusing iron into other elements, whether within a star or within a laboratory pulls more energy from the reaction than it creates. It is the first element in star evolution that does this, and is therefore associated closely with the end-stage of a star's life. The energy has to come from somewhere, and the models I have seen have the star eating up its outer layers very rapidly. Perhaps within a day, which we would have noticed. [Edit: I previously stated this as fusing elements into iron whereas it has been correctly pointed out that it is iron fusing into other elements that is the problem.]

For further evidence we can look at other stars whose makeup we know to be primarily iron through spectroscopy and compare them and their systems to ours.

In general, any useful theory needs to make definite predictions (and bonus points if they differ from the standard model) that can be either confirmed or refuted by observation and experimentation. If I knew more about this 'Iron Sun Hypothesis', I could refute it better, but as it stands, it disagrees with enough of what we believe we know that it requires overwhelming evidence before most will pay it any attention.

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    $\begingroup$ I don't think that's correct. My understanding is that fusion reactions creating elements up to and including iron produce energy, and fusion reactions past that absorb energy (which is why elements past iron are produced mainly in supernova explosions). Thus a massive old star could be producing iron in its core. When the inputs to that process run out, the star collapses because fusion stops being exothermic. $\endgroup$ – Keith Thompson Oct 6 '14 at 18:26
  • $\begingroup$ I was going mostly off of 30 year old college learning, so I did some searching based on your response just to be sure. Here is an article that talks about it. My understanding is that the star uses up all of its energy in the production of iron, so it can't get to heavier stuff before going nova or just collapsing. This episode of AstronomyCast is another good source of info. $\endgroup$ – IchabodE Oct 6 '14 at 18:38
  • $\begingroup$ I think the article is consistent with what I wrote. "At 3 billion degrees, the core can fuse silicon nuclei into iron and the entire core supply is used up in one day." So silicon-to-iron fusion produces energy, but only lasts about a day; once the silicon is depleted, the iron can't be fused any further without consuming energy. (The jump from Si, atomic number 14, to Fe, atomic number 26, does seem odd; I clearly don't entirely understand this stuff.) Elements lighter than iron can be fuel for fusion reactions; iron and heavier elements cannot. $\endgroup$ – Keith Thompson Oct 6 '14 at 19:07
  • $\begingroup$ @MBurke, Iron, not silicon, is the last element produced by esothermic reactions see here. Please, rewrite your answer. $\endgroup$ – Py-ser Oct 7 '14 at 7:11
  • $\begingroup$ Fixed, though I couldn't get to your link, I realized that I misspoke. $\endgroup$ – IchabodE Oct 7 '14 at 16:55
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Standard solar models reproduce the sun's mass, radius, luminosity, spectral energy distribution, line spectrum, neutrino luminosity, and vibration spectrum (helioseismological) with great accuracy. The age inferred for the sun lines up nicely with the age of the solar system inferred from isotope ratios in meteors. The solar models are based on the same physics that produces stellar evolution models, which fit the color-magnitude diagrams of clusters of various ages and compositions in impressive detail. In other words, the standard picture of solar and stellar structure is accepted because it explains, in detail, a stupendous amount of richly textured observational detail. Manuel's theory, by contrast, explains nothing in particular.

As a reference, I'd point the interested reader at any of the many excellent astronomy textbooks aimed at the distribution-requirement college courses.

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