The Motion of Stars

Motion in the Sky:  
We know that the Earth moves from East to West on a daily basis. Astronomers use such features of the Earth such as the poles, the equator and the lines of latitude and longitude to help map out the position of the stars. We call this map the Celestial Sphere. It is divided into 24 parts running from the South Pole to the North Pole. The patterns of the stars form what we call constellations. They are found in relatively the same position in the celestial sphere. Of course, the position of the constellation in the night sky depends on the position of the observer on the surface of the Earth. For example, a person in the Southern Hemisphere cannot see the North Star. We also observe that different constellations are seen in different positions during summer and winter seasons. This has to do with the fact that the Sun blocks off the view of certain constellations during the Earth's orbit around it. Despite all these factors, astronomers can still use these constellations to locate a particular star.

The stars, in reality, are moving quite fast in space. As a result, the constellations have been changing very slowly over the years. The Big Dipper is one constellation in which five of the stars are moving one way, while the other two are moving in the opposite direction.