Quoting NASA…. While many of the nebulae visible in the night sky are emission nebulae — clouds of dust and gas that are hot enough to emit their own radiation and light — Caldwell 4, otherwise known as the Iris Nebula or NGC 7023, is a reflection nebula. This means that its color comes from the scattered light of its central star, which lies nestled in the abundant star fields of the constellation Cepheus. Located some 1,400 light-years away from Earth, the Iris Nebula’s glowing gaseous petals stretch roughly 6 light-years across. While the Iris Nebula appears predominantly blue, it includes large filaments of deep red, indicating the presence of an unknown chemical compound likely based on hydrocarbons. Studying nebulae like this one helps astronomers learn more about the ingredients that combine to make stars.