Explanation:
A molecular cloud also called a stellar nursery , is a type of the interstellar cloud, with the composition of commonly the molecular hydrogen ,
In dark clouds , the accumulation of the dust in a specific location , which blocks the starlight and hence , stopping ionization , and thereby making that area dark .
They do not fill all of the intersteller space , because , the number of dust grains only account for a fraction of the volume of the intersteller space .
