Astronomy is learned during the last years of university but it often takes more than 5 years of study to become an astronomer. It is even insufficient because astronomy is so vast that you have to choose a specialty (astrophysics, cosmology, optics, radio astronomy, etc.). Sometimes some students only start working at the age of 25 or 28, having spent most of their youth studying.
Your diploma in your pocket you will be able to work but you will still have to present the result of your researches to become “doctor” in science and to work in an observatory or to teach the students.
If you like teaching you can become a lecturer or teacher and teach most of your time. Most astronomers also have another degree (engineering, aggregation, journalism, etc.) or contacts with companies because sometimes there is no place in observatories or research laboratories. This allows them to continue working while waiting to make a day of astronomy.
For the astronaut the course is sometimes different and a training of military pilot is sometimes sufficient if for example you only want to become pilot or engineer on board the international space station (ISS) or the future shuttles. But in any case all astronauts are engineers, they have a university degree in science or technology. Some, like F. Story Musgrave even has seven university degrees and not least.
If you want to become an astronomer, astronaut or engineer you must love and know math, mechanics and physics because you will use it during your job to make calculations and invent theories that will allow you to better understand the phenomena that you observed and sometimes to predict new events.
On the other hand, if you do not like mathematics or physics, you can still become an astronomer by changing your orientation during your university studies. It’s more difficult but if you learned philosophy for example, you can still change your option and study astronomy and one day become a researcher if you really want to. Check out this article to find out about astronomer and other astronaut formations.
If the university or the work of astronomer does not interest you, the job of animator remains open to you. It is accessible to amateur astronomers or enthusiasts who are very familiar with astronomy. Many regularly appear on astronomy discussion forums. You can also orient yourself towards the job of scientific journalist (editor). But these trades increasingly require a university degree or proof of having worked in this field for several years (as animator, presenter, writer, journalist, columnist, etc.).
So good luck for the future, the sky is so vast that there can be no competition between astronomers!