The Cocoon Nebula, also known as IC 5146 or Barnard 168, is a 4000 light-year distant emission nebula: it’s a stellar nursery. The nebula was first discovered in 1899, and was described as similar to the Triffid Nebula, (Messier 20 in Sagittarius). It is remarkable because there is an absorption nebula behind it, which makes it stand out in a dark region where practically no stars are to be seen. IC 5146 spans on 100² seconds of arc.

The Nebula houses in its womb a star cluster known as Collinder 470, and astronomers have recorded stars as dim as magnitude 17. However the cluster as a whole is approximately magnitude +7.

See you next week for another nebula!
Clement