Astronomy

You want to do a core job or what? Yes, these jobs do need science students but remember that there are material management experts and commerce expert jobs too in these fields. Your question is not clear, but I think that you should do a job in that field to suffice your heart's desire.

Admission to the PG courses will be done on the basis of GATE/JEST/UGC NET.

For space science, please complete M.Sc in physics and PhD also. After that, you can apply for entrance exam of ISRO.

You can try for Punjab Technical University (PTU). It has courses in aeronautics that might interest you. Moreover, the university has great reputation in case you are not eligible for IITs and NITs.

After class 12th, you have so many opportunities:
Aeronautical Engineering
Aerospace Engineering
Astronautical Engineering
Mechatronics
Aircraft Maintenance Engineering

You would be eligible through GATE score and not CAT.