You should be familiar with FORTRAN 95.
Also I'd argue that C++ is more important than FORTRAN for people interested in computational astrophysics. All of the new code is being written in C++ rather than FORTRAN, because everything you can do in FORTRAN you can do in C++ whereas the reverse is not true. There is incredible cutting edge stuff in C++ that doesn't exist in FORTRAN. (look at the boost::math libraries)
Also knowing C++ is like knowing English. It's the standard language for industrial applications.