Astrophysics is a branch of science which utilizes the methods and principles of physics to study the astronomical objects and phenomena. It is a multidisciplinary field which incorporates concepts and methods from many disciplines such as classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics. This subject focuses on the study the Sun, stars, galaxies, extrasolar planets, the interstellar medium and cosmic wave background. The emissions from these objects are analyzed across the electromagnetic spectrum for characterization of properties like luminosity, temperature, density, chemical composition, etc. Astronomical research often involves a substantial amount of work in the field of theoretical and observational physics. Some areas of study under this discipline include determining properties of dark matter, dark energy, black holes, other celestial bodies and the origin of the universe. Observational astrophysics is a sub branch of astrophysics which focuses on the techniques to record and interpret data. This book is compiled in such a manner, that it will provide in-depth knowledge about the theory and practice of astrophysics. The various sub-fields of astrophysics along with technological progress that have future implications are glanced at in it. This book will provide comprehensive knowledge to the readers.