What scientific evidence is there to support or refute the Iron Sun Hypothesis?
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?
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.
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.
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.
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.
That's so removed from evidence currently available that I would not call it a "hypothesis". It has a lot of the characteristics of crackpot science, unfortunately. It's just orthogonal to everything we know about the Sun: density, spectrum, neutrino production, etc.
@FlorinAndrei, personally, I don't believe this theory either - I have had discussions elsewhere online with the Professor himself, and it still did not make sense. By making a question like this, it allows an online searchable record of evidence to refute this theory in an objective scientific manner.
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.
I'm not sure, but I can't see the problem with doing so, provided you make a link back to the question here. It would be good for there to be a really definitive answer to this question from a real expert.
I think, these points are not valid: they proposed for a completely new model. Maybe, the astrosismology point is the only one which can really be an evidence against their theory, but I do not know anything about. @DikranMarsupial, if the answer author could still read this topic we could have a nice discussion.
@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.
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.
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.
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!)
@DikranMarsupial, I think you could retire your answer: people continue to upvote it, but it is wrong... 3 out of 4 of your points are not correct, and the 4th is not supported. About your last comment: why do you mention gravity effects? However, I agree on your point of `not-cited = not-reliable`. But that is *not* a scientific reason per se.
@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.
As to why mention gravity, I would have thought that was fairly obvious, in estimating the density of a star, knowing its mass would be a useful piece of information, and we can estimate that from its gravitational effects (e.g. planetary orbits). If there is a big difference in the density of iron and metalic hydrogen, then this would have big implications on the plausible composition of the Sun's outer layers if the core were primarily iron.
I also disagree with not-cited = not reliable. Science doesn't work that way. Being able to support an argument with citations adds to the reliability, but it certainly isn't zero in the absence of citations, and arguably citing some papers detracts from the reliability of the answer (plenty of papers get published that are simply wrong). For reliability, you really need papers that have been accepted by the research community, for example those that are highly cited. At the end of the day though, it is the evidence and internal consistency that matters.
Sorry if my comments seemed troll-like, I just try to keep it short in the messages. I am not able to write an answer, but this does not prevent me to say which reasons are not good to disprove the theory. As @KeithThompson already explained, many of the points in this answer are not good, like the spectrum one. I think, this is a delicate topic anyway.
@Py-ser there was no problem in the manner in which you comment, the point is that I am genuinely interested in why my answer was wrong so that I can learn (especially as one of the points I made was essentially the same as the comment you made on the original question, which suggest there is some nuance that I have missed).