The central one is Mercury — that is, a Merkabah within a Merkabah, meaning 4 tetrahedrons together.
But it seems like one alone isn’t enough...
You still have to additionally add the 4 other elements — and the question is, how? As triangles or as Merkabahs?
And then the Sun and Moon are also shown separately, also moving toward the center as additions...
So then it becomes:
Moon = Merkabah
Sun = Merkabah
Mercury in the center = two Merkabahs (4 tetrahedrons)
The other 4 planets/stars = either 4 additional triangles (which would form 2 more Merkabahs),
Or each planet is a full Merkabah — so 4 Merkabahs.