What physical property is significantly reduced in a star entering the red giant phase, making its outer layers easier to dislodge?

Answer

Its surface gravity

Because the star expands to immense sizes in the red giant phase, the surface gravity drops significantly relative to the total mass, allowing the outer layers to be more easily expelled.

What physical property is significantly reduced in a star entering the red giant phase, making its outer layers easier to dislodge?
starsstellar evolutionastrophysicsMass loss