Lunar nodes
The two points where the Moon's orbit crosses the Sun's path. Not bodies but crossings: eclipses can only happen near them. Astrology reads the axis as familiar ground versus growing edge.
The Moon's orbit is tilted about five degrees against the ecliptic, so it crosses the Sun's path twice each lap: once heading north, at the ascending or north node, once heading south, at the descending or south node. They are geometric points, always exactly opposite each other, and the axis drifts slowly backward through the zodiac, completing a circuit in about 18.6 years.
Their hard astronomy job is scheduling eclipses, which occur only when a New or Full Moon lands near a node. Their interpretive job is younger and looser: most modern astrologers read the south node as the well-worn and already mastered, and the north node as the direction that feels unfamiliar and asks for growth.
Honesty requires a note here: the tradition disagrees about how much the nodes do. Some practitioners rank them with Jupiter and Saturn as makers of events; others decline to interpret them at all. The nodal return, near ages 19, 38, 57, and 76, is the least contested piece of node lore.