This book is based on a series of lectures for an Astrophysics of the Interstellar Medium (ISM) master¿s degree in Astrophysics and Cosmology at Padova University.

From the cold molecular phase in which stars and planetary systems form, to the very hot coronal gas that surrounds galaxies and galaxy clusters, the ISM is everywhere. Studying its properties is vital for the exploration of virtually any field in astronomy and cosmology. These notes give the student a coherent and accurate mathematical and physical approach, with continuous references to the real ISM in galaxies.

The book is divided into three parts. Part One introduces the equations of fluid dynamics for a system at rest and acoustic waves, and then explores the real ISM through the role of thermal conduction and viscosity, concluding with a discussion of shock waves and turbulence. In Part Two, the electromagnetic field is switched on and its role in modulating shock waves and contrasting gravity is studied. Part Three describes dust and its properties, followed by the main stellar sources of energy. The last two chapters respectively address the various components of the ISM and molecular clouds and star formation.

Fundamental equations for ideal fluids.- Acoustic waves.- Real fluids.- The interstellar medium.- Shock waves.- Turbulence.- Electrodynamics and magnetohydrodynamics.- Motion of a plasma in a magnetic field.- Magnetohydrodynamic waves.- Dust from the interstellar medium.- HII regions.- Stellar Winds.- Supernovae remnants.- The interstellar medium and its components.- Molecular Clouds.- Star formation.

Giovanni Carraro earned his initial degree in astronomy at the University of Padua in 1991, and then completed his Ph.D. at that same institution in 1996 with a thesis on the formation of elliptical galaxies. He followed up this achievement with two post-doctoral fellowships, one at SISSA/ISAS in Trieste and the other at Yale University. The '00s and the first half of the '10s had him taking on a series of posts as Visiting Scientist at a significant number of universities, many of them in the USA. while spending 9 years as support astronomer at ESO Paranal, Chile. He has written extensively on the subject of astronomy, including having had 325 papers published in peer-reviewed journals, 82 as primary author. He has been involved in many astronomy-related organizations, including serving as Vice President (2009-2012) and President (2012-2015) of IAU Commission 37 (star clusters and associations). Throughout his career, he has maintained his commitment to scientific education and presently holds a position as Associate Professor at his alma mater. He is the director of the PhD school in Astronomy and also serves as scientific editor of AAS journals.His current personal research involves studies of Open and Globular clusters (in relation to the formation of the Milky Way and Local Group galaxies) and the outer solar system bodies and Uranus/Neptune satellites (in the context of the origins of satellite systems and the taxonomy of said bodies).