Small Dark Nebulae.

Abstract

Attention is drawn to the small, round, dense dark nebulae with diameters varying between 5Y and 10'. We propose that these be named "globules." The regià n of Messier 8 abounds in globules. Published photographs show at least sixteen of them projected against the bright background of the diffuse nebula. At the derived distance of 1260 parsecs for Messier 8, the diameters of twelve of the sixteen observed globules are between 10,000 and 35,000 AU. It is noteworthy th~t there is no evidence for globules in the region of the Orion nebula. At least twenty of the dark objects in Barnard's lists are true globules. A preference is shown for the regions of Sagittarius and Ophiuchus and for the Scutum Cloud, but some isolated examples of large globules (with diameters of the order of 100,000 AU.) are found in the anticenter region. The estimated minimum absorptions for the small globules are 2-5 mag. The larger globules are more transparent (1 mag.)