When a red giant reaches the end of its life, it casts off its
outer shell of matter while its core collapses into a white dwarf. The shell expands outwards
at incredible speeds (tens of kilometres per second), forming a distinctive type of nebula, the
planetary nebula. Planetary nebulae can take the form of simple rings or 'bubble' shapes (like the
Ring Nebula in Lyra), or more complex spiralling
forms, such as that shown by the Cat's Eye Nebula in Draco.