Can scientists become astronauts?

which countries? ...i want to become an astronaut. i am preparing for isat exam ( entrance exam for undergradute programs in iist on completion of which students are absorbed in isro) but india in its 1st manned mission (2015) is selecting only indian air force pilots. the reason for choosing vyomanauts ( indian word for astronaut) from the pool of IAF fighter pilots is that they are already trained to endure high gravity forces. This makes it easier to train them for space missions. i guess nasa does send scientists in space. do u see india doing the same in future? any other way i can become an astronaut? go for nasa? i'll feel betrayal for my country if i go there