अपनी Milky Way Galaxy की Black Hole इतनी तकतवार है

In the solar system of the milky way galaxy, earth was supposed to have been formed about…… billion years back

The Sun, which is 2.2 xx 10^20 m from the center of the Milky Way galaxy, revolves around that center once every 2.5 xx 10^8 years. Assuming each star in the Galaxy has a mass equal to the Sun's mass of 2.0 xx 10^30 kg, the stars are distributed uniformly in a sphere about the galactic center, and the Sun is at the edge of that sphere, estimate the number of stars in the Galaxy.

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) .