This book lays the essential foundation of what is known as astrophysics, the study of the nature and physics of stars and their systems. The sciences of astronomy and physics have been intertwined since the 17th century when Sir Isaac Newton introduced the laws of motion and the universal law of gravitation. Readers will draw connections between these two critical fields of science and in doing so, will gain an enriched understanding of the theoretical framework for interpreting astronomical observations. This eBook discusses a variety of topics in contemporary astrophysics including black holes, dark matter, dark energy, evidence of the big bang, and the recently discovered existence of exoplanets.