Bright Nebulae

Bright nebulae are dense clouds of interstellar gas and dust that are visible because they are illuminated by nearby stars, making them appear as glowing objects in the night sky.

Bright nebulae occur in two main classes depending on their source of illumination: emission and reflection, although they occasionally are a combination of the two. A less common third type of the bright nebula is the supernova remnant.

Emission nebulae are clouds of dust and glowing hydrogen gas, sometimes referred to as H II regions. The atoms in the cloud are ionized by nearby hot stars, a process which releases energy in the form of visible light and this type of nebula typically appear red in images.

Reflection nebulae shine as a result of the dust in the nebula scattering starlight from a nearby star or stars (the gas does not actually reflect any light), and typically, reflection nebulae appear blue in images.

A supernova remnant is the remains of a catastrophic stellar explosion, wherein much of a star’s material is ejected. Their appearance can be similar to emission nebulae and they often appear as a highly structured cloud.