<p>Get a physics degree as an undergraduate and take as many astronomy or astrophysics courses as you can. There are no astrophysics B.S. degrees and your only other option is astronomy as a B.S. A physics degree is more general and will offer you more opportunities for careers after you graduate. If you decide that your path is to get a graduate degree in astronomy or astrophysics, a B.S. in physics is perfectly fine as a starting point.</p>