Figure 1-14 The Seasons Earth’s axis of rotation is inclined 23½° away from the perpendicular to the plane of Earth’s orbit. The north pole is aimed at the north celestial pole, near the star Polaris. Earth maintains this orientation as it orbits the Sun. Consequently, the amount of solar illumination and the number of daylight hours at any location on Earth vary in a regular pattern throughout the year. This is the origin of the seasons.