Scope of astrophysics?

There aren't a lot of jobs in the field, and almost all of them require a PhD in astronomy or physics. Try the PhD in physics instead; you can do other things with that. Many people spend 8-12 years in college to get a PhD in astrophysics and then have to leave the field because there aren't enough jobs. Most NASA jobs require you be a US citizen; they do hire foreign students as postdocs (temporary research positions) but those are extremely competitive. It won't make you rich, but most astrophysicists live comfortably.