The Cocoon Nebula (IC 5146/Caldwell 19), is a star-forming nebula in the constellation Cygnus, roughly 3,000 light years away. The bright, rounded nebula is about 15 light years across, and its name comes from the way it looks like a glowing cocoon wrapped in dust. It is both an emission nebula, where hydrogen gas glows red under ultraviolet radiation, and a reflection nebula, where starlight scatters off fine dust to create soft blue and white tones. The energy comes from a hot, young star at its center that carved out the cavity in the surrounding gas, and the whole region is only about a million years old. The nebula sits at the end of a long, dark lane of dust known as Barnard 168, which stretches off to the left and looks like the trail of a comet.