Iris Nebula. Optical image of NGC 7023, the Iris Nebula (blue, upper centre). North is at top. This reflection nebula is the part of a cloud of gas and dust that is glowing blue from the reflected light of a bright, hot, young central star. The rest of the nebula is dark and is seen silhouetted against the surrounding stars. This nebula is around 6 light years across and is about 1300 light years from Earth in the constellation Cepheus.