What critical element causes the stellar fusion engine to shut down in massive stars?

Answer

Iron (Fe)

The fusion process hits an absolute chemical wall when the core begins producing iron, as this is the heaviest element synthesized through normal stellar fusion processes.

What critical element causes the stellar fusion engine to shut down in massive stars?

#Videos

Why Do Some Red Giant Stars Explode As Supernovae? - YouTube

astronomystellar evolutionsupernovaastrophysicsexplosionred supergiantred supergiants