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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.


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