 FACT: The prologue narrator refers to stars and regions of gas  between them, then says that "the starlight makes the gas  transparent, and where there are no stars, it appears as dark  obscuring clouds." Transparency is actually caused not by starlight  but by the absence of dust; starlight will either have no effect on  the appearance of gas, or will cause it to be illuminated or perhaps  to fluoresce. Dark obscuring clouds are those that contain dust and  are not illuminated.