Astrophysics is the physics of stars, and more broadly, the physics of the universe. It allows us to understand the structure and evolution of planetary systems, stars, galaxies, interstellar gas, and the cosmos as a whole.

In this concise introduction, leading astrophysicist James Binney describes the rapid expansion of the field of astrophysics in the past century, thanks to the enormous amounts of data collected by telescopes that have explored all regions of the electromagnetic spectrum and the rapid increase in computing power, factors that have allowed increasingly effective mathematical models to be developed. The author explains how the application of the fundamental principles of physics - regarding energy, mass, and momentum - together with the two pillars of relativity and quantum mechanics have led to a substantial understanding of phenomena ranging from rapidly rotating pulsars to the collision of giant spiral galaxies. This is an accessible and scientifically accurate introduction to astrophysics at a basic mathematical level, for readers who want to engage with the fundamental concepts of the field.