Barnard 72 is the famous "Snake" or "S" dark nebula in Ophiuchus. It is a concentration of obscuring dust and dark matter in space that is opaque and doesn't let the stars behind show through it. Below and to the right of the Snake is B68, an extremely dense dark nebula, and to the lower left of it are B69, B70 and B71. These dark nebulae get their name from pioneer astrophotographer Edwin Emerson Barnard, who cataloged many of them photographically, publishing a list in the 1919 paper in the Astrophysical Journal, On the Dark Markings of the Sky with a Catalogue of 182 such Objects.