Is it possible to become an astrophysicist later in life?

I see alot of people at my college who are middle aged or older than the average student. I was wondering how hard it is to get into a phd program in astrophysics once you have been out of school (working) for a few years. I am a senior majoring in economics. I have taken general physics (excellent grades), introductory C++, general chem, higher level mathematics (linear algebra, differential equations). I know that acceptance to phd programs in astronomy or astrophysics depend on research experience as well. Its not a concrete goal of mine but just something i think of in case i want to do something else with my life later on. How will be my chances of getting into a good program after working for a few years? (provided i take any pre requisite cles in physics etc, i do not have any research experience in physics).