Hi Deepika,

After 12 standard, You should apply for bachelors degree of Astrophysics  in reputed/Top universities in Canada or United States. After 4 years of course, You can apply for masters degree for 2 years and PhD for 2 more years followed by apprenticeship under great supervision. You become a scientist.

Apart from studies you have to complete test pilot program from a recognized pilot school. Astronauts required atleast 2 years of work experience as pilot for jet fighter aircraft or 1000 hours of flight certifications.

while undergoing all this you already hold PR (permanent Residence) for any of the above country and it will take more than 8 -10 years to complete all the above studies and you can apply for American or Canadian Citizenship. After All this studies you can apply for Astronaut in NASA, where you have to undergo many medical test and you have pass each and every single test. once you done with all this .. then you are ready to fly in zero gravity. But one thing its way too high risk then applying in Armed forces. So if you decided to be next Neil Armstrong, Kalpana Chawla or Sirisha Bandla. Go ahead . All the best . hope this information helps you to become astronaut and travel to space.

Thanks.