As you did 12th withwPCMB,you have wide scope for career. You may opt for MBBS as it has good carrier opportunities. But you have to study so do what your heart says and do things which you enjoy.  Cosmologist should have deep passion for  Physics, Astronomy and Mathematics which  has to inspire you to learn things on your own . Area such as aerospace engineering is typically the minimum requirement to get an entry-level job in cosmology such as Research Assistant with starting salary of  30,000 per month. Whereas experienced and qualified professionals can demand salary ranging from Rs. 10 lakhs per annum to around Rs. 12 lakhs per annum.