The general theory of relativity has allowed a better understanding of the structure of the universe. One of the fundamental problems in the general relativity is finding exact solutions of the Einstein field equations. Some solutions found fundamental applications ins astrophysics, cosmology and more recently in the developments inspired by string theory. Different mathematical formulations that allow to solve Einstein´s field equations have been used to describe the behaviour of objects submitted to strong gravitational fields known as neutron stars, quasars, and white dwarfs. General relativity also allows the analysis, through Einstein's gravity theory, of different cosmological scenarios as the existence of dark energy, dark matter, Phantom and Quintessence fields that were introduced to explain the accelerated expansion of the universe. An astronomical object or celestial object is a naturally occurring physical entity or structure that exists in the universe.
In this book, our main goal is to inform latest knowledge about stellar objects and its importance in both astrophysics and knowledge of Cosmology. One of the most advantages about writing this book is to make a connection between mathematical formulation of these phenomena associated with its practical and applied concepts in the universe. The study of stellar objects helps to understand more concepts in the universe such as the reason and nature of forming Black holes and other related aspects in Astronomy and generally in cosmology. We study about stars and their nature. Also, we make a connection between concept of stellar objects with whole concepts of General relativity presented by Albert Einstein.