Interface: Planetary Nodes (BK-05)

Astrology is all about nodes. Nodes are sensitive points in the natal chart that can be interpreted. Obvious examples of nodes are the Nodes of the Moon. The Ascendant, Midheaven, Vertex and other sensitive horoscope points are nodes. The traditional twelve House Cusps are also nodes. Since most astrologers do not consider latitude when calculating aspects, even aspects are nodes. We may be familiar with the above nodes, but what about planetary nodes? What are they?