I wanna change my career from 'Software Testing' to 'Astronomy'?

Am pretty confused! I always wanted to have a career in Astronomy or aerospace or in Aeronautical Engineering. It has been my interest. I have done my B.E in mechanical engg, am 23 now and working as a software tester. I wanna change my career now. Please advice. Is this viable. If so what shoudl i do. Is there anyone whoc have changed their career from software line to Aerospace. Please Help