Since I was a young child I always
You have some redundant words here... it might be better not to include "always," because you used "since."
If you make the whole first para all about liking to learn new things and research them, etc., then it is really a theme that anyone could use... anyone could claim to have this energy for learning... but you can distinguish yourself if you make the first para focus on astronomy, not the theme of liking to learn new things.
I like the anecdote about middle school!
But this should be replaced:
Earlier I mentioned my interest in learning new things, my proverbial "thirst for knowledge". I believe this is why I appreciate astronomy so much. All this stuff... it adds nothing new to the essay. For every para you write, make sure the reader has a distinct experience. How about replacing it with some references to serious articles and books you have recently read about astronomy...
:-)