What physical structure results from massive stars sequentially burning heavier elements in their cores and shells?

Answer

An onion-like structure composed of concentric shells, each burning a different element

As heavier elements are fused sequentially (hydrogen, helium, carbon, etc.), the star develops distinct burning zones layered concentrically around the core, creating an onion-like structure.

What physical structure results from massive stars sequentially burning heavier elements in their cores and shells?
Elementastronomystarmassnucleosynthesis