these names keep popping up but i don't even know who they are why are they so significant ?

only been playing since Morrowind are they from dagger fall or earlier ?

Magnus is the Sun. If I recall correctly, he's the greatest of the Aedric spirits that (pretty angrily) left Nirn and went back to Aetherius as soon as they realized that they were fooled by Lorkhan. The "Sun" you see in the game is nothing more than a hole to Aetherius that was made by him in Oblivion (which is the darkness of the night). The stars are the holes that the lesser spirits also did then they left.

Lore:
http://www.uesp.net/wiki/Lore:Shalidor#Shalidor
http://www.uesp.net/wiki/Lore:Magnus_%28god%29#Magnus