What is a planetary nebula made of?
Planetary nebula is the gases that are shed from the outer layers of a red giant star in its final stages.
A star like our sun expands to red giant at the end of its main sequence, and the outer layers are puffed out into space, drifting outward. This gas forms the planetary nebula.
The nebula is this made of the gases found in the outer layers of a red giant - hydrogen, helium, carbon, nitrogen and oxygen.