The Angelic Orders and the Tree of Life.

We know from the Scriptures that there are Nine Orders of the Angels. These are: Angels, Archangels, Virtues, Powers, Principalities, Dominations, Throne, Cherubim and Seraphim. (Click here to see more)

St. Paul was the first to acknowledge these Orders in his writings to Ephesians and the Colossians; from this we can determine that St. Paul recognised Nine Orders in total. Those indicated above and in the table below.
It was Cornelius Agrippa, who assigned these Nine Orders of Angels to the Kabbalistic Tree of Life, as follows:

From the perspective of the Pauline Art the above table is important as it indicates the particular Angelic Order associated with each of the traditional planets.

But what about the Primum Mobile and Starry Heaven? Well, in medieval astronomy, the Primum Mobile, or "first moved," is the outermost moving sphere in the universe. Astronomers believed that the seven naked-eye planets (including the Moon and the Sun) were carried around the spherical Earth on invisible orbs, the Universe.

The Starry Heaven is the area which is between the planets and the Primum Mobile. The ancient Greek philosophers believed in a stationary Earth, which was the center of the Universe. At night they observed the stars which appeared to revolve in a circle around a point in the northern sky. They concluded that the heavens were in continual circular motion. From this observation they reasoned that the stars must be attached to a rigid heaven that held them fixed in the sky (in which the planets revolved), so that their positions did not change relative to one another as the sky turned.

Naturally this may seem a little ridiculous with the astronomical knowledge that we today possess. What the ancients were trying to do, which is still relevant today, is to identify those areas within our Solar System, were they believed the angels had dominion over.

What the table does tell us is that at the top of the tree is the Universe (Primum Mobile) the outer most mechanism which makes our total Universe revolves. Between the traditional planets, which can be observed to move independently in variable orbits, and the The Primum Mobile is the area known as the Starry Heavens, where the star are held in fixed positions by the heaven.

References:

De occulta philosophia libri tres (Three Books of Occult Philosophy,) by Cornelius Agrippa (1486-1535), published in Cologne 1533.