What element's creation in the core signals the definitive end of a star's ability to generate energy via conventional fusion?

Answer

Iron

Fusion continues through heavier elements until the core produces iron, because fusing iron atoms consumes energy rather than releasing it, causing the outward pressure support to vanish.

What element's creation in the core signals the definitive end of a star's ability to generate energy via conventional fusion?

#Videos

How Stars Die - YouTube

deathastronomystarstellar evolutionsupernova