Schematic illustration showing how the asterism called the Big Dipper (in the constellation Canis Major, or the Great Bear) changes with time. Top left shows how the pattern appeared 100, 000 years ago. In the middle is the present-day positioning. And the bottom shows how the stars will be arranged 100, 000 years from now. The changes are due to the stars' proper motions - their movement across the sky as they orbit the Milky Way hub.ement across the sky as they orbit the Milky Way hub.