Old French astronomie, from Latin astronomia, from Ancient Greek ἀστρονομία (astronomia), from ἄστρον (astron, “star”), from Proto-Indo-European *h₂stḗr (“star”) + νόμος (nomos, “arranging, regulating”), related to νέμω (nemō, “I deal out”).
astronomy (plural astronomies)
- The study of the physical universe beyond the Earth's atmosphere, including the process of mapping locations and properties of the matter and radiation in the universe.
Usage notes 
- The study of the physical processes which control matter and energy in the universe is commonly called astrophysics. The investigation of the origin, evolution, and fate of the universe itself is called cosmology.