Sh2-112 (also informally known as the Nautilus Nebula) is a circular HII emission nebula located approximately 5,600 to 6,800 light-years away in the constellation Cygnus. Situated about 1.5 degrees from the bright star Deneb, this region of ionized gas is a hive of active star formation within the Orion Arm of the Milky Way. The nebula is primarily energized by the massive O-type blue double star BD+45 3216, which emits intense ultraviolet radiation that causes the surrounding hydrogen gas to glow a deep red. Spanning roughly 15 to 25 arcminutes in the sky, Sh2-112 is characterized by a prominent north-south dark dust lane that bisects its western side, creating a “blister” morphology where the central star appears to have carved a cavity into the parent molecular cloud.  Written by Gemini AI.