Nebulae

Galactic nebulae are vast clouds of gas and dust found within the interstellar medium of a galaxy. They play a central role in stellar evolution and occur in a variety of forms.

Emission nebulae are ionized by high-energy radiation from nearby hot stars, causing the surrounding gas to emit its own light, while reflection nebulae do not emit light themselves but reflect the light of nearby stars. Dark nebulae consist of cold gas and dust and appear as light-absorbing structures silhouetted against brighter background objects, whereas planetary nebulae and supernova remnants represent late stages of star evolution – from shells of gas ejected by dying sun-like stars to the expanding remains of powerful stellar explosions.