Cosmochemistry refers to the study of the chemical makeup and composition of the universe. There are several synonyms one can use to describe this area of study. Astrochemistry is one such word, referring to the chemical processes and elements present in celestial objects such as stars and planets. Another synonym is extraterrestrial chemistry, which focuses on the chemical reactions that occur outside of the Earth's atmosphere. Planetology is yet another synonym, describing the study of the formation and evolution of planets, including their chemical composition. Finally, one can use the term space chemistry, which specifically refers to the study of chemical reactions that occur in outer space.