The main factor that shapes the life and eventual death of a star is how much mass it began with. A star that is 2.8 times the mass of our sun will most likely end up as a white dwarf. When medium size stars are near the end most of the hydrogen core has been changed to helium. The helium core then begins to shrink and as this happens the core heats up. The energy that is released by the core heating up causes the the outer hydrogen shell to expand greatly. As the shell expands it cools and the colour changes to red. The helium core will continue to heat up until the helium atoms start to fuse to form carbon atoms. When all the helium is fused to carbon it begins to die and gravity causes the last of of the star's matter to collapse inward forming a white dwarf.
