Becoming an astronomer is not easy at all. You need to get several good GCSE grades and you might study up to the age of 24, at university.
You should therefore aim to do well in as many GCSE subjects as possible, but the ones which will be most important are Mathematics, Physics and any other science.
Subjects like Modern Foreign Languages, Computer Science and Geography can be very useful.
You also have to make sure that you get good grades in English as you will always need to be able to write well.
