What is the suggested origin of pockets within nebulae that are strongly enriched in heavy elements but deficient in hydrogen?

Answer

Expulsion of deep, hydrogen-poor core material

The existence of pockets strongly enriched in heavy elements but simultaneously deficient in hydrogen suggests that these regions originated from deep within a star where the final, heavy-element-rich core material was expelled.

What is the suggested origin of pockets within nebulae that are strongly enriched in heavy elements but deficient in hydrogen?
SpaceastronomycompositionstarsElementsstellar nebula