Can a commerce student have any possibility of becoming an astronaut or studying astronomy?

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 astronom

There seems no possibility of becoming an astronaut or studying astronomy being a commerce student as being a astronaut requires a master's degree in a STEM (Science, Technology, Engineering, Mathematics)

Where as Astronomy courses are based on a combination of Physics, Chemistry, and Mathematics, so