When the sun reaches the end of released into space, forming a life cycle, the expanded part will be Planetary nebula.
Step-by-step explanation:
Planetary nebula formed after when the external layer is shredded due to running out of fuel so that it can burn. This external layer of gas expand into the space, the shape of nebula can often be ring shaped or even a bubble. At the centre of this nebula it has the shinning left over middle part of the star. This star can also be seen. The temperature of the nebula is 100000C. The planetary nebula last for about 10000 years between its formation and the recombination.