Sh2-155: The Cave
Nebula
Back after the government shutdown, NASA’s Astronomy Picture of the Day
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 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.
