That doesn't give any evidence that there is only one sun. There can be more than one sun in a dimension. Heck, every one of the stars could be suns.
So you're saying there could be more than one Magnus-spirit up there, but the people on Nirn, which is the center of the Universe, does not experience for some reason, but other places do?
Are you even aware of what the sun is? I really think you are, because I'm certain I've seen you talk about it. But now, I don't know. Anyway. It's not a giant ball made out of burning gas. It's a hole.
As for "ever star could be suns", you're absolutly right. Stars are also holes to Aetherius, but much smaller ones. No burning gasballs. Small holes.
With modern techniques, we almost certainly know a lot more about the universe than a few wizards and daedra worshippers would know about their universe. I'm not making up a version, I'm just applying RL cosmology as a possibility.
And last time I checked, no one took a lot of things in modern cosmology seriously when they were first envisioned.
People in TES has enough technology to have much more knowledge about their universe than we could know about us. They've sent people into both Oblivion and Aetherius several times.
Visit to Aetherius occur even less frequently than to Oblivion, for the void is a long expanse and only the stars offer portal for aetherial travel, or the judicious use of magic. The expeditions of the Reman Dynasty and the Sun Birds of Alinor are the most famous attempts in our histories, and it is a cosmic irony that both of them were eventually dissolved for the same reason: the untenable expenditures required to reach magic by magicka. Their only legacy is the Royal Imperial Mananauts of the Elder Council and the great Orrery at Firsthold, whose spheres are made up of genuine celestial mineral gathered by travelers during the Merethic Era.
http://www.imperial-library.info/pge3/arena_supermundus.shtml
edit: Of course, there's always the possibility that the TES world is just myth, legend and lies. All of it. It could be just like our world, and, for example, men, mer, argonians and everything inhabiting the planet could have evolved into what they are. Dark Elves was not changed into what they are by Azura's curse, they evolved into it! "The survival of the fittest" ensured that only the ones with thick skin survived. The skins became so thick they became gray. And so on, and so forth. I've put out that theory before, just for fun at that time, but no one really listened?
Why? Because it's not really that fun. It's not as interesting as TES would be if all the myths and legends and lies were true.