Figure 1-15The Seasons Are Linked to Equinoxes and Solstices The ecliptic is inclined to the celestial equator by 23½° because of the tilt of Earth’s axis of rotation. The ecliptic and the celestial equator intersect at two points called the equinoxes. The northernmost point on the ecliptic is called the summer solstice; the southernmost point is called the winter solstice.