What causes the cessation of core fusion in a star like the Sun?

Answer

Hydrogen in the core is entirely converted into helium.

Core fusion stops because the star's primary fuel, hydrogen, located in the very center of the core, is completely used up and converted into helium ash.

What causes the cessation of core fusion in a star like the Sun?

#Videos

Why Do Red Giant Stars Get Bigger? - YouTube

astrophysicsred giantstar evolutionmain sequence star