A supergiant star can keep adding shells to its core "onion" structure until it produces uranium as a byproduct.

Question

Quizplus · Accepted Answer

Supergiant stars can add shells in their core structure and produce elements up to iron through nuclear fusion, but elements heavier than iron, like uranium, are generally formed through other processes such as supernova nucleosynthesis or neutron star mergers, not by fusion in a star's core.

A Supergiant Star Can Keep Adding Shells to Its Core