Figure 22-17: The Rotation of Our Galaxy Each schematic diagram follows three stars (the Sun and two others) orbiting the center of the Galaxy at different distances from the galactic center. (a) This case of stars with similar, nearly uniform, orbital speeds is what we have in our Galaxy. Although they start off lined up in this illustration, the stars become increasingly separated as they move along their orbits. With a uniform speed for all stars, stars inside the Sun’s orbit overtake and move ahead of the Sun, while stars far from the galactic center lag behind the Sun. (b) The stars would remain lined up if the Galaxy rotated like a solid disk. This orientation is not what is observed. (c) If stars orbited the galactic center in the same way that planets orbit the Sun, stars inside the Sun’s orbit would overtake us faster than they are observed to do.