As this excellent book demonstrates, the study of comets has now reached the fas cinating stage where we understand comets in general simple tenns while, at the same time, we are uncertain about practically all the details of cometary nature, structure, processes, and origin. In every aspect, even including dynamics, a choice among several or many competing theories is made impossible simply by the lack of detailed knowledge. The space missions, snapshot studies of two comets, partic ularly the one that immortalizes the name of Sir Edmund Halley, have produced a huge mass of valuable new infonnation and a number of surprises. Nonetheless, we face the tantalizing realization that we have obtained only a fleeting glance at two of perhaps a hundred billion (lOll) or more comets with possibly differing natures, origins, and physical histories. To my personal satisfaction, comets seem to have discrete nuclei made up of dirty snowballs, as I concluded four decades ago, but perhaps they are more like frozen rubbish piles.

The study of Comet Halley in 1986 was a tremendous success for cometary science. In March of that year, six spacecrafts passed through Comet Halley as close as 600 km from the nucleus and made the in situ measurements of various kinds. These space missions to Comet Halley and that of the ICE spacecraft to Comet Giacobini-Zinner combined with studies, both ground-based and above the atmosphere, have increased our knowledge of cometary science in a dramatic way.This new edition of Physics of Comets incorporates these new and exciting findings. The emphasis of the book is on the physical processes operating in a cometary environment. It discusses up-to-date observations, methods and results based on the study of various comets. The subject is developed in a systematic manner covering various aspects of cometary phenomena. This book may serve as a text book for students, and as reference material for researchers.

This book provides a comprehensive overview of our current knowledge of comets. It presents a fascinating survey of the study of comets throughout history, from antiquity to the present day, and includes the most recent discoveries on the exceptional comets Hale-Bopp and Hyakutake. The authors discuss the role of comets in the formation of our Solar System and describe the links between comets, asteroids and the recently discovered Kuiper-belt objects. The book also includes new insights into the composition and nature of cometary nuclei, with results from the most up-to-date observation techniques. Written in a clear and lively style, and beautifully illustrated, this book will appeal to anyone interested in comets and astronomy, professionals and amateurs alike. It will be of particular interest to students and researchers in astronomy, astrophysics and planetary science, as well as general readers with a good background in physics.

Written by a leading expert on comets, this textbook is divided into seven main elements with a view to allowing advanced students to appreciate the interconnections between the different elements. The author opens with a brief introductory segment on the motivation for studying comets and the overall scope of the book. The first chapter describes fundamental aspects most usually addressed by ground-based observation. The author then looks at the basic physical phenomena in four separate chapters addressing the nucleus, the emitted gas, the emitted dust, and the solar wind interaction. Each chapter introduces the basic physics and chemistry but then new specific measurements by Rosetta instruments at comet Churyumov-Gerasimenko are brought in. A concerted effort has been made to distinguish between established fact and conjecture. Deviations and inconsistencies are brought out and their significance explained. Links to previous observations of comets Tempel 1, Wild 2, Hartley 2, Halley and others are made. The author then closes with three smaller chapters on related objects, the loss of comets, and prospects for future exploration. This textbook includes over 275 graphics and figures – most of which are original. Thorough explanations and derivations are included throughout the chapters. The text is therefore designed to support MSc. students and new PhD students in the field wanting to gain a solid overview of the state-of-the-art.

Comets are small bodies, but of great cosmic relevance. Given its pristine nature, they may preserve valuable and unique information on thechemical and physical processes that took place in theearly solar system, and that may be occurring in the formation of other planetary systems. They might have even played a very important role in the origin of life on Earth. Beyond that, since ancient times comets have inspired awe, superstition, and also curiosity anddebate. Their sudden apparitions challenged the long-held view of the immutability of the heavens, which triggered a long debate on whether comets had a heavenly or terrestrial nature. Therefore, comets have a prominent role in the history of scienti?cthought, that goes back to the most ancient civilizations. The last apparition of comet Halley in 1986 was a landmark since it arouse a great expectation in the scienti?c community and in the public at large. For the ?rst time, a ?otilla of spacecrafts visited a comet. Agreat number of popular and technical books were written on Halley, and comets in general, around the mid-eighties. The interest in comets never subsided after Halley’s passage which is re?ected in the large volume of printed material on these bodies. I have taken the challenge to write a new book on comets that summarizes most of the recent advances on thesubject, including my own workdeveloped during the last 25 years.

Radiating fire and ice, comets as a phenomenon seem part science, part myth. Two thousand years ago when a comet shot across the night sky, it convinced the Romans that Julius Caesar was a god. In 1066, Halley’s Comet was interpreted as a foreshadowing of the death of Harold the Second in the Battle of Hastings. Even today the arrival of a comet often feels auspicious, confirming our hopes, fears, and sense of wonder in the universe. In Comets, P. Andrew Karam takes the reader on a far-ranging exploration of these most beautiful and dramatic objects in the skies, revealing how comets and humanity have been interwoven throughout history. He delves into the science of comets and how it has changed over time; the way comets have been depicted in art, religion, literature, and popular culture; and how comets have appeared in the heavens through the centuries. Comprehensive in scope and beautifully illustrated throughout, the book will appeal not only to the budding astronomer, but to anyone with an appreciation for these compelling and remarkable celestial bodies.

Although the development of ideas about the motion and trajectory of comets has been investigated piecemeal, we lack a comprehensive and detailed survey of ph- ical theories of comets. The available works either illustrate relatively short periods in the history of physical cometology or portray a landscape view without adequate details. The present study is an attempt to review – with more details – the major physical theories of comets in the past two millennia, from Aristotle to Whipple. My research, however, did not begin with antiquity. The basic question from which this project originated was a simple inquiry about the cosmic identity of comets at the dawn of the astronomical revolution: how did natural philosophers and astronomers define the nature and place of a new category of celestial objects – comets – after Brahe’s estimation of cometary distances? It was from this turning point in the history of cometary theories that I expanded my studies in both the pre-modern and modern eras. A study starting merely from Brahe and ending with Newton, without covering classical and medieval thought about comets, would be incomplete and leave the fascinating achievements of post-Newtonian cometology unexplored.