which is the suitable subject to study in astronaut related career? guide me

Necessary qualifications vary from country to country. On paper, most space organizations state that astronauts require a bachelor’s degree. Realistically speaking, however, potential astronauts must go through extensive and rigorous training.
Most organizations that hire astronauts provide training themselves. The training often involves the trainee using simulation software to learn how to conduct effective space research, and how to survive in outer space.
There is also a minimum and maximum height and weight requirement for a job like this. Other physical and medical tests are also done before one is able to become an astronaut. Training is essential in this kind of job, and there are strict government regulations in most countries requiring this extensive preparation.