At what age should i look at college?

It's never too soon to start thinking about college. I had the same plan at your age - studying astronomy at a top school. And a few years later I learned that an astronomy major doesn't prepare you for grad school in astronomy and there aren't any jobs in astronomy if you don't have a PhD, so you really need a bachelors in physics instead (and often a PhD in physics as well). And then I found out that no matter how good your grades are and what impressive things you've done, there's still only a very tiny chance of getting into those schools, so I picked a liberal arts school that I loved instead, and still went on to grad school, finishing a PhD now, and I've got a job lined up at a top institution. So it's fine to dream, but eventually you might have to be a bit more realistic - and that's OK, because you can still do well at schools you hadn't considered or even heard of at your age.