Sh2-155 (Cave Nebula)

Constellation: Cepheus

Distance: 2900 Light Years

The Cave Nebula is an H II emission nebula, energized and illuminated by young, mostly blue O and B stars emerging from the hydrogen cloud. The stars being formed belong to the Cepheus OB3 association, and are very young, mostly less than 100,000 years old. Interstellar dust blocking light from the nebula and stars causes the dark "cave", within which several pre-main sequence stars are seen. (Information from A Year in the Life of the Universe by Robert Gendler, and The 100 Best Astrophotography Targets by Ruben Kier).