Nightscapes & Deep Sky Colors
Astrophotography © Brian A. Morganti
Sh2-155 - Cave Nebula
Complex of Dark - Bright - Reflection Nebula
Shown Below is 50% crop view of Cave Nebula
About 2,400 light-years away, this scene lies along the plane of our Milky Way Galaxy toward the northern constellation of Cepheus. This wonderfully complex star forming region in the constellation Cepheus includes bright Hydrogen emission nebulae, blue reflection nebulae, yellow reflection nebula close to a variable nebula, and dark nebulae. The bright central emission nebula is classified as Sharpless2-155 (Caldwell 9), which surrounds what is popularly called the "Cave Nebula" which carves out the bright red nebula in the center of the image. The brightest of the three blue reflection nebulae is vdb155 located near the bottom right of the main image above. The very dark nebula located above vdb155 and to the right of the red emission nebula is LDN1216.
The region itself is quite complex as well, containing several different nebulae of various types. First and foremost, we have a dim, but exceptionally bright diffused emission nebula, which in this case, is shrouded by thick pockets of interstellar dust. It alone has a radius of about 35 light-years! To put this in perspective, the closest planetary system to Earth – the Alpha Centauri triple star system – is located more than 4 light-years from Earth. Light would could go from our solar system to Alpha Centauri and back four times before light could make a one way trip from one side of this nebula to the other.
Secondly, we have a star formation region that is shaped like a crescent. It is comprised of doubly ionized hydrogen molecules. This ionization is caused by stars embedded in Cepheus B; a molecular cloud located on the outskirts of the region. The stars within the Cave Nebula are very young, mostly less than 100,000 years old, while new stars are born at a high rate within the dust clouds of the nebula. Two bright stars (HD 217061 and HD 217086) illuminate the bright ridges of the Cave Nebula. Visually, the Cave Nebula would be a very difficult target to see even with the aid of a 4" refractor using a medium power eyepiece and a UHC filter from a dark sky location.
Astrophotography - Nightscapes & Deep Sky Colors