Molecular Cloud Barnard 68 . ... What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud . ... One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above . ... It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. ...