The “Interstellar Medium” (ISM), the material between stars, is explored in this book as a dynamic ecosystem vital to star formation and galactic evolution. Rather than empty space, the ISM acts as both a stellar nursery, providing raw materials for new stars within molecular clouds, and a graveyard, receiving remnants from dying stars. Understanding the ISM, with its varying densities, temperatures, and chemical compositions, is crucial for grasping how galaxies evolve. This book begins by tracing our understanding of the ISM’s historical observation and then investigates the ISM’s dynamics, including the turbulence, magnetic fields, and stellar feedback that influence star formation. The book highlights the ISM's composition of gas and dust and its various ionization states. It emphasizes the ISM's role in the formation of planetary systems and the chemical enrichment of space, drawing from radio, infrared, and X-ray observations, including data from space-based observatories. The book is structured in three parts, progressing from the ISM's fundamental properties to its dynamics and broader galactic implications. By synthesizing observational and theoretical work, “Interstellar Medium” provides a comprehensive overview of the ISM, a valuable resource for those seeking to understand this active participant in galactic ecosystems.
