If the Sun's mass is about average, how many stars are there in the Milky Way galaxy? The mass of the Sun is of the order of 10^30 kg and the mass of the Milky Way galaxy is of the order of 10^42 kg.

Answer 1

You divide Milky Way mass (1 x 10^42 kg) by Sun's mass (as the average of 1 x 10^30 kg) to get 1 x 10^12 average stars. This about one trillion stars.