LDN 557 Dark Nebula
Constellation: Sagittarius
A dark nebula or absorption nebula is a type of interstellar cloud that is so dense that it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger molecular clouds.
Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation.
Taken 7/8/18 in Grand Rapids, Ohio by Russell Kille on a CPC 1100 with Hyperstar @ F2 and ZWO ASI294MC Pro camera