Our sun with mass `2 xx 10^(30)kg` revolves on the edge of our milky way galaxy which can be assumed to be spherical having `10^(20)m` Also assumee that many stars identical to our sun are unifromly distributed in the spherical milky way galaxy If the time period of the sun is `10^(15)` second and number of stars in the galaxy are nearly `3 xx 10^((a))` find value of 'a' (take `pi^(2)` = 10, `G (20)/(3) xx 10^(-11)`inMKS) .