Sh2-155: The Cave Nebula
This colorful skyscape features the dusty, reddish glow of Sharpless catalog emission region Sh2-155 , the Cave Nebula. About 2,400 light-years away, the scene lies along the plane of our Milky Way Galaxy toward the royal northern constellation of Cepheus . Astronomical explorations of the region reveal that it has formed at the boundary of the massive Cepheus B molecular cloud and the hot, young, blue stars of the Cepheus OB 3 association . The bright rim of ionized hydrogen gas is energized by the radiation from the hot stars, dominated by the bright blue O-type star above picture center. Radiation driven ionization fronts are likely triggering collapsing cores and new star formation within. Appropriately sized for a stellar nursery, the cosmic cave is over 10 light-years across.