What as an example of a star with a high mass, and how does it go from main-sequence to iron core?

Thank you.

Hello dbte47

The combination of a stable (main-sequence) high mass star and an iron core is rather unlikely.

High mass stars are capable of burning carbon and oxygen and beyond, depending upon their mass. A high mass star may even reach a point where nuclear fusion produces iron. But to do this, energy is not produced but has to be added to the process. Due to the energy need required, the core will collapse under gravitational pressure, and - depending on the mass of the star - will collapse into a neutron star or a black hole. The rest of the star mass will be thrown into space (supernova).