Journey of the Sun Among the Stars

Abstract

Assuming that the Earth is a sphere, we can construct the following model to explain the daily movement of the stars. All stars lie on the surface of an imaginary celestial sphere and this sphere rotates around an axis defined by two fixed points: the north and south celestial poles. In this model, stars’ daily disappearance from view does not mean they are gone; they have just gone below the horizon, outside our line of sight. In Fig. 6.1, we show the paths of three different stars as the result of the rotation of the celestial sphere. Star A is close to the north celestial pole and is always visible to a northern observer. Star B is on the celestial equator; it will rise in the east and set below the horizon in the west. Star C is close to the south celestial pole and can never be seen by a northern observer. As we can see from Fig. 6.1, the altitude of a star above the horizon changes throughout the day. The star will reach its maximum altitude when it crosses the local meridian. For example, star B will rise from point X (intersection with the horizon) and set at point Z (intersection with the horizon) and reach the maximum altitude at point Y where its path intersects with the meridian.