IC 4603: Reflection Nebula in Ophiuchius . ... Dust, minute globs rich in carbon and similar in size to cigarette smoke , frequently starts in the outer atmospheres of large, cool, young stars. ... Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. ... NASA Official: Jay Norris. ...