bright nebula

A bright nebula is a cloud of interstellar gas and dust that emits its own light or reflects the light of nearby stars. These nebulae are composed primarily of hydrogen and helium, with trace amounts of other elements.1

Bright nebulae are further classified into several subclasses:
* Reflection nebulae: These nebulae reflect the light of a nearby star off their dust grains.1
* H II regions: These are clouds of hydrogen ionized by the ultraviolet light from a nearby hot star (O or B type). The ionized hydrogen atoms then emit visible light as they recombine and drop to lower energy levels.12
* Diffuse ionized gas: This is a pervasive component of the galaxy observed through faint emissions.1
* Planetary nebulae: These are expanding shells of luminous gas ejected by dying stars. Despite their name, they are not related to planets but resemble planetary disks when viewed telescopically.13
* Supernova remnants: These are expanding clouds of gas resulting from the explosions of massive stars.1