Our Sun, with mass 2.00×1030 kg, revolves about the center of
the Milky Way galaxy, which is 2.20×1020 m away, once every
2.50×108 years. Assuming that each of the stars in the galaxy has a
mass equal to that of our Sun, that the stars are distributed
uniformly in a sphere about the galactic center, and that our Sun
is essentially at the edge of that sphere, estimate roughly the
number of stars in the galaxy.