Wrong university choice?

You have several options, depending how much time and money you want to spend. For starters, you can switch majors or double major. It might take some extra time, but then you'll be studying what you love. You can also check out the requirements to minor in Astronomy. Depending on how many credits you have left for Archaeology, you might not want to let your studies go to waste. It still might be useful to have that degree someday if you decide Astronomy isn't all it's cracked up to be. You should talk to your advisor or counselor to see what your options are.