Red Giant Stars

Red Giants are very large, cool and luminous stars. This stage lasts about 10% of the stars life. They are old stars meaning they don't have much lifetime left.
The red giant phase occurs in stars, which weigh less than 4 solar masses. The star starts to collapse towards the center causing the star to heat up. The fusion rate increases within the outer shells; this causes the star to expand. The surface cools, making the star turn red. The red color increases causing the star to increasingly expand.
Red giants occur as a result of the hydrogen in the core running out. …