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dangerbird
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how is it known that iron is formed in stars and not anything heavier? And how is it known that elements like uranium arent in fact formed in the cores of stars prior to supernova? answers much appreciated
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Vanadium 50 said:Neither of those statements are true. (Hence the "how is it known" part is superfluous)
so what's the evidence for the idea that elements heavier than iron don't form in the core of a star like al lthe others do? is it an assumption based on the fact that the binding energy of iron is higher than the released energy? is that all the evidence? i can't really think of how to search this through googleVanadium 50 said:Neither of those statements are true. (Hence the "how is it known" part is superfluous)
can solar spectra be used to determine that stars don't form heavier than iron like the rest of the elements? say if someone were to say that in fact elements heavier than iron DO form just like all the others, would there be much evidence or any to prove them wrong?malawi_glenn said:one can measure spectrum of stars and supernovae and find out which and how much elements there are.. how do we know that the sun is made up of mainly hydrogen? Well we look at and analyse the solar spectra...
dangerbird said:can solar spectra be used to determine that stars don't form heavier than iron like the rest of the elements? say if someone were to say that in fact elements heavier than iron DO form just like all the others, would there be much evidence or any to prove them wrong?
DecayProduct said:Elements heavier than iron do form in the cores of stars, otherwise where would they come from?
malawi_glenn said:Supernovae ... r-process
DecayProduct said:Haha! I'm not sure how to read this! I mean, that's what I said further down my post, so I'm not sure if you are correcting me, or confirming me! Haha!
malawi_glenn said:I could not understand the rest of that post, so I thought I just answer that question you posed ;-)
DecayProduct said:Why? Was I that wrong? Or did I just not word it right?
What I was saying is that nuclear fusion reactions can be self-sustaining using any fuel with nuclei less than the mass of iron. Nuclear fusion using elements heavier than iron can take place, but will not be self-sustaining because they actually require that energy be input. I think the terminology is that stars fuse elements exothermically (I said endo- in the other post incorrectly), and releasing energy. So stars with iron fuel cannot keep generating energy by creating elements heavier than iron.
When a star goes supernova, some of the material is slammed into other material at energies great enough to cause elements heavier than iron to form. A sort of grand particle accelerator. Sound correct, or am I totally in the toilet?
dangerbird said:so is the whole idea that stars fuse only up to iron during their lifetimes backed up by solar spectra observations? Or does that idea only come from the fact that anything heavier than iron wouldn't be a self sustaning reaction.
dangerbird said:http://www.nscl.msu.edu/science/nuclearastrophysics/rprocess
heres another page that's saying the making of heaviest elements is still a mystery.
it seems like this is still a mystery malawi but not a total mystery like youre saying
malawi_glenn said:one can measure spectrum of stars and supernovae and find out which and how much elements there are.. how do we know that the sun is made up of mainly hydrogen? Well we look at and analyse the solar spectra...
Chronos said:Extreme temperatures are necessary to fuse heavy elements. It is essentially a matter of forcing enough protons together long enough to acquire the electons necessary to form a stable nucleus. The temperatures necessary to fuse elements heavier than iron/nickel can only be achieved in supernova. While the very early universe was indeed very hot, it lacked one essential ingredient - protons. This is why hydrogen was not formed until the latter stages of the big bang,