In a Reflection nebula, the nebulous material is visible because of the reflect light from nearby stars. In an Emissionnebula, the material making up the nebula is also clearly visible, but because of radiation it produces itself. The nebula's energy is ultimately derived from stars often embedded within its own structure, whose radiation causes ionisation within the nebula, leading to a release of energy visible as light.
The Eagle Nebula, M16, is a prominent emission nebula in the heart of the Milky Way as it passes through the southern reaches of Serpens Cauda. This nebula is a busy star-forming region, estimated to contain more than eight thousand clustered young stars, and the energy from those stars causes the surrounding clouds of gas and dust to glow with light. Imagery provided by Aladin sky atlas
