Getting a job in astronomy such as working for NASA by looking through telescopes to look for planets etc.?

NASA does indeed have telescopes (in space) and they do indeed hire people to reduce and interpret the data from those telescopes. To get that job, you need a PhD in physics or astronomy, and you need to do good research and publish papers while in graduate school. Yes, they hire foreign nationals to work those jobs, both at NASA and through other institutions that work with them in other countries, like the University of Leicester.