Object Analysis

The Cave Nebula (Sh2-155) is a dim and very diffuse bright nebula within a larger complex containing emission, reflection, and dark nebulosity. It is located in the constellation Cepheus, approximately 2,400 light-years from Earth.

Visually, it looks like a deep, dark cavern opening up in the starry background. This "cave" is actually a dark dust lane that obscures the bright emission nebula behind it. The bright rim of the cave is ionized by hot, young stars in the vicinity (the Cepheus OB3 association).

The nebula is difficult to see visually but reveals spectacular detail in long-exposure photography. The curved ionization front is a site of triggered star formation, where the radiation pressure from massive stars compresses the gas to form new suns.