A Double and a Trifid

M20 (The Trifid Nebula)
Sketch by Eiji Kato

M20, The Trifid Nebula, is a famous and beautiful target for astro-photographers. The red emission nebula contains a young star cluster at its center, and is surrounded by a blue reflection nebula that is most noticeable at the northern end. It’s distance is not well agreed upon, and is listed anywhere from 2,200 light years (Mallas/Kreimer) to 9000 light years (Jeff Hester).

The dark nebula that crosses the Trifid was cataloged by Barnard and listed as B 85. The object was originally cataloged by Charles Messier in 1764, when he described it as a cluster of stars. William Herschel assigned catalog numbers to 4 different parts of the nebula (H IV.41, H V.10, H V.11, and H V.12).