Which is what I asked for... among other things.
You want speculation and assumptions?
While that is really the provence of the REers on this board, I will make an attempt. There is a rigid dome, or several domes, made of crystalline aether surrounding the Earth. The otherwise perfect crystalline structure is ocassinally marked by impurities of various concentrations. The impurities marr the crystal structure of the aether which prevents the crystal from being perfectly stable, and as it decays or erodes or otherwise settles into its lowest energy state it emits radiation on wide and varying spectra. The largest of these impurities are the sun and moon. Smaller ones include the other planets and comets. The tiniest -- but by far the most numerous -- are the fixed stars.
It may be that the impurities involve oxygen in their formation, which would explain why the the impurities closer to the Earth (sun, moon, planets) are by far the largest and brightest.
Whoa... that was fun.