Describe the evolution of a star with a mass like that of the sun, from the main-sequence phase of its evolution until it becomes a white dwarf.

After the main sequence phase ends, the star will evolve toward the upper-right area of the H-R diagram as its core contracts and the outer layers expand. It then becomes a red giant and will continue to expand its outer layers. This causes its luminosity to increase, the star's size can become more than 100 times its main-sequence radius. Eventually, the contracting core reaches a temperature of 100 million K, which leads to the explosive ignition of helium. When the star stabilizes, it will lose some of its outer layers as it becomes smaller, and moves back toward the main sequence region of the H-R diagram. The star will continue to fuse helium into carbon and oxygen, but for a time much shorter than the time on the main sequence.

Eventually, the core will be depleted of helium, and the star once more evolves toward the upper-right area of the H-R diagram as the core contracts and the outer layers expand to an even greater extent. The outer layers of the star will be gradually blown out into space by the strong winds during this period. This leads to the formation of a planetary nebula out of the outer layers of the star. The remaining mass of the star in the core continues to contract and will eventually become a white dwarf.

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