![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Ring_Nebula.jpg/640px-Ring_Nebula.jpg&w=640&q=50)
Emission nebula
Nebula formed of ionized gases that emit light of various wavelengths / From Wikipedia, the free encyclopedia
An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emission nebulae are H II regions, in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.[1][2]
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Ring_Nebula.jpg/640px-Ring_Nebula.jpg)