What are Red Giants and White Dwarfs?

A star shines by turning its hydrogen into another element called helium. This change results in heat which keeps the star hot. When its hydrogen fuel runs out the star begins to die and eventually begins to puff outwards like red hot cloud. This is known as the red giant stage. Finally it shrinks into a very hot globe and is known as a white dwarf.

It is believed that if the sun every becomes a red giant the inner planets of the solar system would disappear under its surface. Red giants are very luminous while white dwarfs are dim.