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Iron is the most stable single element in nature(I don't know about combinations of elements, but oh well, not applicable to question). Stars go through cycles where they change the materials of their cores, culminating in iron for the longest lasting and largest stars. The cores of stars naturally have tremendous forces. My question: Has humanity managed to combine two iron nuclei together? and if yes why can we do it but not stars? Alternatively, where would the progression past iron nuclei go, since no element is more stable?

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  • $\begingroup$ Note that the heavier fusion reactions in star cores do not fuse two nuclei of the same kind. Instead, they proceed via the alpha process, which fuses a helium nucleus with a heavier nucleus. Eg, carbon + helium $\to$ oxygen. $\endgroup$ – PM 2Ring May 6 at 22:17
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Iron is the most stable nucleus, so in principle all heavier nuclei are unstable and will eventually decay to iron. However if it occurs at all this process is ridiculously slow. For example fusing two iron nuclei would give a tellurium nucleus, but tellurium is (as far as we know) stable to fissioning into iron. The reason tellurium is stable is because there is a kinetic barrier that the tellurium atom would have to overcome to split into two iron nuclei, and outside of the cores of supernovae the barrier is so high that the process doesn't happen on the timescale of the life of the universe.

Anyhow, elements heavier than iron are made in supernovae. If the supernova was an equilibrium process most of the matter in it's core would convert to iron because that's the lowest energy nucleus. However a supernova is not an equilibrium process so it's possible to get elements that don't appear at equilibrium. At the peak of the supernova the immense pressures can fuse the nuclei of heavy elements, and some of these manage to survive until after the peak pressure falls. That's how all the elements heavier than iron got created.

Mankind has (as far as we know) never managed to fuse two iron nuclei. Colliding iron nuclei in accelerators might momentarily produce a tellurium nucleus, but the nucleus would be in an excited state due to the energy of collision and it would immediately fall apart again. Reproducing the conditions in a supernova is beyond us at the moment.

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  • $\begingroup$ Sidebar knowledge - Iron is the most naturally magnetic element, aka its electrons spin in synchronized orbits. Does this affect stability? Since most of the more structurally sound elements are more naturally magnetic with like 1 outilir *which I don't remember. $\endgroup$ – Evan Mata Feb 2 '13 at 1:29
  • $\begingroup$ Actually most of the heavy elements are actually created from neutron star collisions. $\endgroup$ – Roghan Arun May 6 at 20:02
  • $\begingroup$ @RoghanArun Actually, they aren't. It is possible that the heaviest r-process elements (which are also very rare) are made in neutron star collisions. However, it is true that this answer risks promulgating the myth that heavy elements are made in supernovae. Perhaps half of them are, others are made by the s-process in non-explosive scenarios in lower mass stars. $\endgroup$ – Rob Jeffries May 6 at 22:47
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When iron is created in a star some of the iron is fused into heavier elements. Though most of the iron collapses into a neutron star or a black hole. Humanity has not been able to combine iron nuclei. Things have to be in perfect balance for that to happen.

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