I’m an international student and I’m interested in studying astronomy. I will attend a university in the US after two years(right now I’m studying in a high school in that has an American curriculum). However, the problem is that I’m scared that only US citizens get jobs in this field, am I right or wrong? Also, is it an extremely hard thing to get a job in that field? My parents advise me to have a bachelor in physics and then do a master in astronomy, what do you advise me guys?
I think you should study what you want to study, that is Astronomy. A foreigner with BS (and MS) in Astronomy or Physics will not find a job/employer (who will need to sponsor a work visa) in US. So it does not matter.
The Bureau of Labor Statistics predicts only 400 openings in the US for astronomers during the whole of the ten years 2014-2024 (http://www.bls.gov/emp/ep_table_102.htm). Of the well over 200 different occupations in its comprehensive list I see only 13 with such meager expectations.
A physics degree will give you more job opportunities with a B.S. International students CAN get jobs with a physics degree (this happens all the time with our international physics majors at Illinois Tech), through the Optional Practical Training route. This allows a STEM graduate to work in the U.S. for up to 36 months after graduation. In that time a lot can happen.
You should be able to take Astronomy courses as electives in a Physics program but an alternative degree might Astrophysics which will allow you to have the astronomy but also a good physics background. My guess is that an MS in astronomy is not all that useful but if you choose to pursue a PhD then your job opportunities are probably the same as for a physicist with a PhD.