Several IITs offer programs related to astrophysics and nuclear engineering, primarily through their Physics departments, though some have dedicated programs as well; to get into these fields, you need to pursue a B.Tech in Physics and then opt for specialized M.Tech or Ph.D programs in astrophysics or nuclear engineering, with admission based on your performance in the JEE Advanced exam followed by further departmental selections.

IIT Bombay, IIT kanpur has specifically these programs you can get it by scoring good marks in JEE advanced.choose physics as your main subject to gain knowledge in field of astrophysics or nuclear engineering.