Cometography is a four-volume catalog of every comet observed throughout history. Volume II provides a complete discussion of every comet seen during the nineteenth century. Cometography uses the most reliable orbits known to determine the distances from the Earth and Sun at the time a comet was discovered and last observed, as well as the largest and smallest angular distance to the Sun, most northerly and southerly declination, closest distance to the Earth, and other details to enable the reader to understand the physical appearance of each well-observed comet. The book also provides non-technical details to help the reader better appreciate how the comet may have influenced various cultures at the time of its appearance. Cometography will be valuable to historians of science as well as providing amateur and professional astronomers with a definitive reference on comets through the ages.

The study of comets is a field that has seen tremendous advances in recent years, far surpassing the knowledge reflected in the original Comets volume published as part of the Space Science Series in 1982. This new volume, with more than seventy contributing authors, represents the first complete overview of comet science in more than a decade and contains the most extensive collection of knowledge yet assembled in the field. Comets II situates comet science in the global context of astrophysics for the first time by beginning with a series of chapters that describe the connection between stars and planets. It continues with a presentation of the formation and evolution of planetary systems, enabling the reader to clearly see the key role played in our own solar system by the icy planetesimals that were the seeds of the giant planets and transneptunian objects. The book presents the key results obtained during the 1990s, in particular those collected during the apparition of the exceptional comets C/Hyakutake and C/Hale-Bopp in 1996-1997. The latest results obtained from the in situ exploration of comets P/Borrelly and P/Wild 2 are also discussed in detail. Each topic of is designed to be accessible to students or young researchers looking for basic, yet detailed, complete and accurate, information on comet science. With its emphasis on the origin of theories and the future of research, Comets II will enable scientists to make connections across disciplinary boundaries and will set the stage for discovery and new understanding in the coming years.

In Part Based on Reviews Presented at the 121st Colloquium of the International Astronomical Union, held in Bamberg, Germany, April 24-28, 1989

Since 1967. the most prominent events of a General Assembly of the International Astronomical Union are published in a separate volume. The Highlights of Astronomy (volume 9) report on the major scientific presentations made at the XXIst General Assembly July 23-August 1. 1991. Buenos Aires. Argentina. The present volume contains the texts of the three invited Di scourses and of the papers presented duri ng seven Joi nt Discussion Meetings and eight Joint Commission Meetings. The invited Discourses were arranged by the IAU Executive Committee and the Joint Discourses and Commission Meetings by the respective chairpersons. The overall responsability of the General Assembly was carried out by the IAU General Secretary (19B8-1991). Dr. D. McNally. I am indebted to the authors of the invited Di scourses. to the organi zers and editors of the scientific sessions for having provided me with all the material for publication in due time. I want to particularly acknowledge the case with which Dr. J.H. Hughes. who unfortunately died a few days ago from cancer. prepared and checked unti 1 the 1 ast few weeks the report on the new IAU Reference System. This report itself concludes long and difficult discussions among IAU members that he led in a wise and clear sighted manner.

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.

In 1993, the U.S. Department of Defense declassified information dealing with frequent explosions in the upper atmosphere caused by meteoric impact. It is estimated that impacts have occurred of a magnitude equivalent to the atomic bomb detonated at Hiroshima. Not all such space voyagers meet their end in the atmosphere, however; huge craters attest to the bombardment of earth over millions of years, and a major impact may have resulted in the extinction of dinosaurs. An impact in Siberia near the beginning of this century proves that such events are not confined to geologic time. Hazards Due to Comets and Asteroids marks a significant step in the attempt to come to grips with the threats posed by such phenomena. It brings together more than one hundred scientists from around the world, who draw on observational and theoretical research to focus on the technical problems related to all aspects of dealing with these hazards: searching for and identifying hazardous comets and asteroids; describing their statistics and characteristics; intercepting and altering the orbits of dangerous objects; and applying existent technologies—rocket boosters, rendezvous and soft-landing techniques, instrumentation—to such missions. The book considers defensive options for diverting or disrupting an approaching body, including solar sails, kinetic-energy impacts, nuclear explosives, robotic mass drivers, and various propulsion systems. A cataclysmic impact posing a threat to life on Earth is a possibility that tomorrow's technology is capable of averting. This book examines in depth the reality of the threat and proposes practical measures that can be initiated now should we ever need to deal with it.

These are exciting times for exobiology. The ubiquity of organic molecules in interstellar clouds, comets and asteroids strongly supports a cosmic perspective on the origin of life. Data from both ground-based telescopes and the recently launched Infrared Space Observatory are providing new insight into the complexity of carbon-based chemistry beyond the Earth. Meteorites give us solid evidence for extraterrestrial amino acids, and putative fossil evidence for life in a 3.6 billion-year-old Martian meteorite hints that life in our system might not be the sole prerogative of the Earth. Giant planets have now been discovered orbiting other stars, and although such planets seem unlikely to be habitable themselves, their existence strongly suggests what many astronomers have long believed - that planetary systems are commonplace. All these topics are reviewed in this volume by active researchers. The level is appropriate for graduate students in astronomy, biology, chemistry, earth sciences, physics, and related disciplines. It will also provide a valuable source of reference for active researchers in these fields.