We should also pause on the symbolism that involves Mary as the door of heaven (Janua coeli) or heaven’s gate (Porta coeli), which we find in many places but notably in St. Peter Damien’s hymn:
“The Virgin pregnant with the Word,
Becomes the door of Paradise:
She has brought our God to earth
And opened Heaven’s gate to us.”
This is closely connected to the scene in St. John’s Apocalypse where we find Mary, “a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars.”
In order to fully understand this symbolism we would need to delve into ancient cosmology or, more appropriately, astrology, but we can summarize the meaning as follows:
The ancient cosmology included seven ‘heavens’ or planetary spheres. We find this arrangement in Islam, Judaism, Christianity (for example, in Iraneus), and in Hinduism (although here they are elaborated in a dual aspect, totaling fourteen in all).
These seven spheres are depicted in ascending order, often as concentric circles with earth as the center, and is the symbolic basis for the geocentric model of the solar system, legitimate in this respect.
In this system, the first point of division is the moon, and what is below is therefore called the ‘sublunary’ world. The sublunary world is subject to the conditions of becoming, namely time and change, in contrast to the higher spheres (of the other celestial bodies and the sun), which are share in a heavenly permanence. In this system, the moon was called Juana coeli, or the doorway to heaven, denoted its station as the point of transition from the terrestrial plane to the eternal.
Thus, we can see that in the imagery above, Mary enables the connection between the sublunary (‘the moon under her feet’) and the celestial worlds.
This is closely connected with other of her epicleses, such as the “Morning Star” and the “Star of the sea,” these referencing the pole star and signifying her position as stationary (unchanging), central (around which all other things revolve), and superior (transfigured substance).