I find it somewhat darkly amusing that I have yet to find a plausible in-fiction explanation for all those moons, or planetoids, or something in the skies of Midchilda, that does not eventually boil down to "it's MAGIC".
Over at TVTropes it's mentioned under Alien Sky, which notes the improbability of this arrangement, as well as suggesting that it is done for the sake of looking cool. The AnimeSuki thread, a dark lair in which the back and forth of spirited debate has mutated into an unholy writhing mass of personal attacks, and for which such matters are destined, hemmed and hawed over the problem for a few pages, before finally utilizing the Gordian solution with the proclamation that it is, indeed, workable only by magic.
The final verdict, I believe, is "moons made entirely of liquid mana". Which end up somehow projecting themselves, or perhaps alternate dimension variants of themselve, or even alternate dimension variants of the planet they revolve around, several times over. Judging from visual evidence, we may find at least six such globes in the sky at any given moment, each one possessing what seems like an atmosphere of its very own.
Later, we are told that Midchilda has two moons in its orbit, each tracing an elliptical path that enables a sort of mystical concordance Just In Time for the events in the show to unfold in the most dramatic manner. Perhaps there are more heavenly bodies that the projection removed from the screen, for ease of significance; we may never know.
It is truly a world of magic, where the laws of gravity and astrophysics are rather more like guidelines. Of such things do we fanfiction writers have to grapple.