Actually, in narrative writing, as you were doing, you should use consistent tense. So you were correct to use "was," as the sun was a star back then, independent of the fact that it also is now.
That's probably why it just came naturally to me because I do read quite a bit and may have seen this word arrangement many times before. My subconscious mind were just spitting out words as I write them. English is only my second language though, I am so much better in Filipino.....lol
