the "diameter" (in "number of stars wide") 10^21 / (4*10^16) = 2.5* 10^4 "stars" area of disc = pi r^2 = 3.14* (1.25 *10^4)^2 =aprx 4.3 * 10^8 star-sq(in "number of stars-squared") height = 10^19 / 4*10^16 = 2.5*10^2 stars high volume = A*h = (4.3 * 10^8)*(2.5*10^2) = 10^11 stars