The Red Giant(Super Giant)Phase
When all hydrogen in the core is gone, an imbalance between the energy force in the core and gravitational force forms. This causes the core to contract and, in turn, the temperature rises. When it gets hot enough, it causes fusion of hydrogen atoms in the shell surrounding the core. The temperature continues to rise, and with that, the star expands, but as it expands, the surface is gets further away from the hot core and begins to cool. Because the star has grown, it gives off light at a constant rate. (a shine not a twinkle) The core is still shrinking and getting hotter, while the surface is continueing to expand and cool. Once the core reaches a temperature of 100 million degrees C°, the helium atoms in the core begin to fuse into carbon and oxygen atoms at a rapid rate. As soon as all the helium has been fused, there is an imbalance between the forces and gravity starts to put pressure unpon the star. The temperature rises in the core and the helium shell around the core starts to fuse and the hydrogen shell surrounding it also begins to fuse into helium. The stability of the star will turn on and off as the atoms in the core fuse and cause fusion amoung the outer shells. Depending on the size of the star this is either called a Red Giant or Red Super Giant. A Red Giant is less then 8 times the size of the sun and a Super Giant is over 8 times the size of the sun.
Next Stage: Formation of Planetary Nebula
