A red giant star, especially
if it is on the asymptotic giant branch, emits large portions of its
envelope into space. The ionization of this emitted material by UV radiation from the hot
core that is left behind leads to beautiful planetary nebulae, and
the hot core becomes
a white dwarf when all its nuclear fuel is exhausted. Thus, white dwarfs and planetary nebulae
are the typical end result of stellar evolution for stars that become red giants.