There are peoples who look up the sky every time and analyze it even at nights. These peoples are called as astronomers. This study of astronomy is called as astronauts.
These astronomers study the space looking for stars, planets, comets etc
And some of them keep watching the space faraway using telescope which is available in both handy size and also in the size of bus, and some of them being laboratories, analyze the rocks (meteorites) and sample which they have brought from moon and other planets.
Some of them do this as a hobby and they are called as armature astronomers
The word astronomy is derived from geek (Which means star or arrangements)