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.

• 对于密度较低的尘埃云来说，尘埃的选择性反射（优先反射波长较短的蓝色光）特性就显得十分重要，因此我们看到的是被蓝光包围的反射星云。