This textbook introduces the reader to the study of astrophysics through a journey that spans the fields of physics, mathematics, and technology. Based on the author¿s extensive teaching experience, it emphasizes the fundamental observational data and theoretical methods employed for constructing models of stars, galaxies, and large-scale structures in the universe. After an introduction outlining the historical development of universe studies, Part I delves into gravitational theories including basic general relativity and gravitational waves. Part II explores radiation and plasma processes crucial for interpreting observed data and modeling cosmic objects. Part III addresses the observational techniques essential in astrophysics, along with the analysis of astrophysical parameters obtained from photometry and spectroscopy.

Attilio Ferrari was Professor Emeritus of Astronomy and Astrophysics at the Faculty of Sciences of the University of Torino, Italy until his passing in 2022.

Professor Ferrari served as Director of the Astronomical Observatory of Torino from 1986 to 2001. During this period, he was a member of the board of directors of the National Consortium of Astronomy and Astrophysics CNAA (1996-2001) and the Istituto Nazionale di Astrofisica - INAF (2000-3). Throughout his career, he contributed to numerous scientific boards. He served as President of the Inter-University Consortium for Space Sciences and also President of the Torino Museum of Astronomy and Space Science. In 2012, he was recognized with the Bruno Rossi Prize (High Energy Astrophysics Division, American Astronomical Society) as a member of the AGILE Team.

Professor Ferrari's research interests encompassed a broad spectrum, including theoretical models of the energetics and morphology of extragalactic radio sources and active galactic nuclei, numerical simulations of nonlinear hydrodynamical and magneto-hydrodynamical supersonic flows from active stars and galaxies and accretion disks, and high-energy plasmas in astrophysics and in fusion machines. He authored over 250 scientific papers in international journals and two textbooks.