Planetary nebula
Planetary nebula is an expanding shell of ionized gas ejected from a low- or intermediate-mass star during the late stages of stellar evolution. It is illuminated by radiation from the remaining stellar core.
Planetary nebulae are discussed in astrophysics, stellar evolution, and observational astronomy.
Status
Planetary nebulae are observed across multiple wavelengths, including optical and infrared. Models of their formation, morphology, and interaction with the interstellar medium continue to be refined.