The Lights and Planets
Pluto
Pluto stands free of the channel and marks the fact that
this process is not just a straight line (Saturn), not just a
tangent (Uranus), and not just an embracement
(Neptune), but a very fine curve wrapping around the
sphere, endlessly repeating the entire process, a "we
are our own grandpa" sort of thing: Very sensitive stuff.
Summary: The only purpose of this diagram is to point
out that all of the planets work together as one great
system, each with their own particular role to play. In
other words, there is only one continuous process
taking place, and the symbol for this entire process is
the Sun.