Okay, so if there's a way to search topics, I haven't found it, so I apologize if this is a repeat.
We know that Remnant's moon rotates to alternately show and hide its shattered side, but that it doesn't go through the phases of our moon (full moon, half moon, new moon, etc.). This suggests that the moon gives off its own light, rather than reflecting the light of the sun.
So... what if the moon is entirely made of Dust, and all of the Dust in Remnant fell there when the moon shattered? After all, Dust often glows.
Of course, it usually glows when it's being activated by Aura, so, I dunno.