Let me try to develop more my intuition:
This site give an overview of the life of a star:
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www.astronomytoday.com/cosmology/evol.html
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This model of stellar evolution is the standard one teached in university. It's base on years of observations.
Basicaly their is two case:
Sun size star: Contract from a cloud. Gravity create at the core a pression and a temperature that start fusion of H to He. The star go in the main sequence for bilion of years. The mass of the star determine the time spent in the main sequence. The more massive star burn faster. During this time the force of gravity is stopped by the radiation: the star keep the same~ size.
When all H is converted to He The core continue to collapse and high enough presure and temperature to start to fuse He. The outer layer is inflated by the rebound of this collapse and by the new reaction. The star become a red giant. The core will continue to collapse to fuse other element until it's all carbon for sun size star. The core will start to cool down becoming a white draft .
Second case a star of 10 solar mass.
Follow the same evolution but go further in the fusion up to the iron.
Iron can not fuse and give energy. It's the most stable nucleus. So their's no energy to stop gravity. The core colapse to nuclear density, and the rebound of the infalling matter create heavier element than iron and the shock wave give us a supernova.
For simplicity let assume that the starting cloud is 100% H.
1- We start with 1 solar mass of H. And we end up to an expanding cloud of H, He .... plus a carbon core, plus energy.
2- 10 Sm of H -> an expanding cloud containing all kind of element and a neutron core and energy.
This kind of system will continue to enrich the space with metal.
Let examine how a supernova can break down iron. The energy release of the collapse can be used in two ways:
fuse heavier element than iron
or break iron nucleus to ligther elements.
