Draw a concept map using the words: Universe, Galaxies, Milky way, Solar System, Sun, Planets, Natural satellies or Moons, Asteroids, Comets, Meteoroids, Moon, tides, Inner planets, Outer planets, Rings, Phases.
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.
