SOLAR SYSTEM

Detailed explanation-1: -In a red giant, the inner helium core contracts while the outer layers of hydrogen expand. When the helium is gone, the stars become white dwarfs. A star like the Sun stops fusion and shrinks into a white dwarf star . A white dwarf is a hot, white, glowing object about the size of Earth.

Detailed explanation-2: -As the core collapses, the shell of plasma surrounding the core becomes hot enough to begin fusing hydrogen itself. As fusion in this shell begins, the extra heat causes the outer layers of the star to expand dramatically, and the surface extends up to several hundred times beyond the former size of the star.