Astronomer

As you are an 11th class commerce student, yes you can become an astronaut or study astronomy. It's not very late as you are in 11th only. So to get into the field of astronomy, you are adviced to change your subject in 12th only so that you do not face any problem in pursuing Bachelor's in astronomy. After that you can complete Masters in fields like MSc Astronomy etc. So yes, you still have chances of becoming an astronaut. 

Yes, you can pursue an M.Sc. in Astronomy after completing a B.Tech in Aerospace Engineering. Many institutions, such as IIT Indore and IIST Trivandrum, accept B.Tech graduates for their M.Sc. programs in Astronomy and Astrophysics.

Admission Requirements:

IIT Indore: Requires a Bachelor's degree in any engineering field or a B.Sc. in Physics/Mathematics.

IIST Trivandrum: Accepts B.Tech graduates with relevant experience in Astronomy and related fields.

Ensure to check specific entrance exam requirements, such as JAM or GATE, for admission.

A degree in aerospace engineering or aeronautical engineering will be an advantage for Indian Astronauts. Students must have essential knowledge of Science (PCM and geology. Nasa hires engineers with a master's degree or a doctorate in aeronautical engineering or a related field, and minimum of 5-10 years of experience in aerospace field.