What do I do if I eventually want a PhD in astrophysics?

[ausername1]

First of all, my GPA isn't that great-I should have put in much more effort than I have and it is the end of my sophomore year. I'm not sure yet about what topic in astrophysics I want to study (it's all equally fascinating at this point) but I do want a Ph.D. in it...
That being said, should I look into Ph.D. programs or masters programs and then get a Ph.D.? Is it easier to get into a masters program than a Ph.D. program if my gpa is low?
I also have questions about grad school abroad, specifically in Australia, should I create an entirely new thread for that topic?

 

[Lavabug]

Put in the effort.

You only need a masters if the university you're applying for a phd explicitly requires it (or if you're trying to compensate for poor undergrad grades, but you still have time to correct this), which the usual deal with European and (afaik) Australian universities.

A 3.0 is the minimum expected at most programs, but some ask for as much as 3.2 and 3.5 minimum. Apply to all the summer research positions under the sun when the next application season comes, and ask for volunteer research work from profs in your department any chance you get. This will expose you to research and better inform your grad school and thesis topic decisions and boost your chances of getting in (and more importantly, reading + working with papers teach you a whole lot more than courses do IME).

Don't wait until your 4th year to get involved in research, you'll find opportunities to do this (and getting paid) are much scarcer after graduating, REU's are only available to students who are still enrolled.