Astronomy is a study of Celestial bodies outside the atmosphere of Earth in deep space, it basically deals with the motion, position, composition, and size of the celestial bodies. Examples of such heavenly bodies are Moon, Sun, Planets, Dwarf planets, Comets, Stars, Meteors, and Galaxies etc.
Astronomy was started in the very recent time in human history when people started looking at the sky filled with twinkling stars and shining moon. They try to guess the mystery behind this beauty of nature, in order to do so they started studying their position throughout the year and made maps of the sky. Many astronomers had the complete chart of positions of stars which they have made with naked eyes. With the invention of the telescope, the astronomy picked up the speed and it developed in the four centuries and reached the modern level. This is mainly observational but theoretical work is also not very less.
Astrophysics is the branch of astronomy that deals with the theories behind astronomical phenomena. It studies the chemical composition of stars and galaxies based on the laws and theories of the physics. Nuclear astrophysics deals with the synthesis of various nuclei inside the stars and predicts the theoretical possibilities of various nuclear reaction. It retraces the evolution of the universe, its present, and past chemical composition. The age of the universe and stars is also calculated by this branch. It resolves the mystery of black holes, neutron stars and pulsars etc. It uses Einstein’s General Theories of Relativity to use the gravitation Lansing for the study of farthest galaxies. It tells us that universe is expanding and the speed of galaxies with respect to each other is continuously increasing. These types of phenomena are studied under the astrophysics.
Therefore, through these examples, we can say that astrophysics is a modern astronomy that’s why the difference between astronomy and astrophysics is not so clear. Astrophysics involves more theoretical work as compared to observational work but it is still incomplete without observations. In past, astronomy was limited to only looking and measuring the position of stars. With the developed of the modern science, astronomy is also becoming modern in the form of astrophysics.