A pinwheel nebula is a nebulous region in the shape of a pinwheel.
Contents
Spiral galaxies
The term 'Pinwheel nebula' is an antiquated misnomer used by observers before Edwin Hubble realized that many of these spiral shaped nebulae were actually 'island universes' or what we now call galaxies.
Wolf-Rayet nebulae
Some Wolf-Rayet stars are surrounded by pinwheel nebulae. These nebulae are formed from the dust that is spewed out of a binary star system. The stellar winds of the two stars collide and form two dust lanes that spiral outward with the rotation of the system.
References
Pinwheel nebula Wikipedia(Text) CC BY-SA