Research Starter on AstronomyAstronomy is the study of objects and phenomena in the universe beyond Earth’s atmosphere. Cosmology is a related science devoted to studying the universe as a whole. There are two main branches of astronomy, observational and theoretical, and several subfields of each, as well as specializations with both observational and theoretical components.
Astronomy Encyclopedia by 
Encyclopedia of the History of Astonomy and Astrophysics by 
