Over the years I've observed that people are often confused about how space and astronomy are used as categories. Obviously they are related and pretty much overlap. However, in popular usage, they refer to fairly different things.
Space is a place you go. It describes an enviroment and is occupied by an industry, mostly government-based, that involves engineering, rockets, satellites, spacecraft, and such.
Astronomy is a science. It's the study of things above the earth's atmosphere (well, okay, things in space). Astronomy involves scientists, telescopes and observatories, theories, data and computer programs.
You could make a good case for the distinction being artificial, but it is real. Space and astronomy involve two very different cultures, in the same way that physics and astronomy are two different cultures, although most astronomy is physics.