"Era tempo che un’opera in italiano fosse consacrata interamente alle galassie, spiegando in modo semplice e accessibile a tutti ciò che conosciamo. È quello che è riuscito ad Alessandro Boselli, specialista di formazione stellare nelle galassie, il quale utilizza, oltre alle sue proprie osservazioni, i dati dei satelliti astronomici.

Astronomy enthusiasts will all appreciate the detailed yet easily-assimilated description of star clusters, how they were formed as our Milky Way galaxy, how they evolved, and how they are classified. The latest research has revealed a vast amount of fascinating information about the clusters, along with some spectacular photographs.

This book summarizes the gathering of information on and the growing understanding of M33 from the 1920s, when Hubble first determined its true nature, to the 21st century, when the Hubble Telescope probed deeply into its many secrets. With its regular symmetrical spiral structure, and its being not tilted too much and near enough to allow detailed studies of its stars, M33 is well-suited for the study of a typical spiral galaxy.

xxii CONTENTS In 1957 I was invited to work on special problems in Magnetic Laboratory of the Academy of Sciences of USSR as a Head of Department of Magnetic Hydrodynamics. In few years this Laboratory was transfered into the I. V. Kurchatov Institute of Atomic Energy, and I continued to work in this Institute up to 1965. In parallel I also worked at Moscow State University as Professor in the CR and Space Research Team. I also gave lectures in Irkutsk, Alma-Ata, Nalchik, Tbilisi, Erevan, Samarkand, and others places. Over about 40 years of teaching under my supervision more than hundred graduate students and scientists in USSR and some other countries gained their Ph. D. and several tenths became Doctors of Science. As my hobby I continued to work in CR research, and as Vice-President of All-Union Section of Cosmic Rays and Radiation Belts, took an active part in preparing the Soviet net of CR stations to the IGY (International Geophysical Year, 1957-1958): we equipped all soviet stations in USSR and in Antarctica with standard cubic and semi-cubic muon telescopes and with neutron monitors of IGY (or Simpson’s) type. In connection with preparing for the IQSY (the International Quiet Sun Year, 1964-1965), the soviet net of CR stations was extended about two fold and they were equipped with neutron super-monitors of IQSY type (with an effective surface about 10 times bigger than the previous monitor of IGY type).

This Atlas provides a complete set of images of Local Group Galaxies (excluding the three for which identification atlases are already in print) and shows the most important objects, including many thousands of individual stars and interstellar objects.

This book deals with stars during a short episode before they undergo a ma­ jor, and fatal, transition. Soon the star will stop releasing nudear energy, it will become a planetary nebula for abrief but poetic moment, and then it will turn into a white dwarf and slowly fade out of sight. Just before this dramatic change begins the star has reached the highest luminosity and the largest diameter in its existence, and while it is a star detectable in galaxies beyond the Local Group, its structure contains already the inconspicuous white dwarf it will become. It is called an "asymptotic giant branch star" or "AGB star". Over the last 30 odd years AGB stars have become a topic of their own although individual members of this dass had already been studied for cen­ turies without realizing what they were. In the early evolution, so called "E-AGB"-phase, the stars are a bit bluer than, but otherwise very similar to, what are now called red giant branch stars (RGB stars). It is only in the sec­ ond half of their anyhow brief existence that AGB stars differ fundamentally from RGB stars.

Galaxy collisions are the key process in building galaxies, triggering the formation of stars and the build-up of heavy elements that allow the formation of planets and solar systems. This book presents the revolutionary research advances achieved in the last decade and lucidly explains the underlying dynamical processes.