C 4

Caldwell 4, also known as the Iris Nebula, is a reflection nebula in the constellation Cepheus.. It spans roughly 6 light-years, glowing bluish from scattered light of its central star, with deep red filaments indicating unknown hydrocarbon-based compounds.

The apparent magnitude is 7.0. Its distance from Earth is approximately 1,400 light-years. Alternate names include NGC 7023. This nebula is of interest for its colors revealing all of the star-forming ingredients.