The Formation of Planetary Nebula
As the surface area increases, the surface gravity decreases causing the outer layer of the star to blow off at an incredible rate. A star can lose up to 80% of its mass during this stage. This mass is the gasous cloud you see surrounding what is left of the central star. This is the core. This star is the hottest star know because the heat from the core is now all that it left, but it is also one of the dimmest stars because it is so small.
