The Trans-Neptunian Solar System is a timely reference highlighting the state-of-the-art in current knowledge on the outer solar system. It not only explores the individual objects being discovered there, but also their relationships with other Solar System objects and their roles in the formation and evolution of the Solar System and other planets. Integrating important findings from recent missions, such as New Horizons and Rosetta, the book covers the physical properties of the bodies in the Trans-Neptunian Region, including Pluto and other large members of the Kuiper Belt, as well as dynamical indicators for Planet 9 and related objects and future prospects. Offering a complete look at exploration and findings in the Kuiper Belt and the rest of the outer solar system beyond Neptune, this book is an important resource to bring planetary scientists, space scientists and astrophysicists up-to-date on the latest research and current understandings. - Provides the most up-to-date information on the exploration of the Trans-Neptunian Solar System and what it means for the future of outer solar system research - Contains clear sections that provide comprehensive coverage on the most important facets of the outer Solar System - Includes four-color images and data from important missions, including New Horizons and Rosetta - Concludes with suggestions and insights on the future of research on Trans-Neptunian objects

The changing character of the IAU General Assemblies becomes most clear from a comparison of the agenda of the Brighton meeting with that of one of the earlier meetings. The fourth General Assembly (Cambridge Mass. , 1932) had about 240 participants, registered guests included, the Brighton meeting had about 2300 people attending. The Cambridge meeting lasted 5, working days, of which, however, three half days were exclusively devoted to excursions, leaving four real meeting days. At that time the nearly 30 commissions had each only one meeting, during part of a morning or afternoon; some commissions did not meet at all. There was one public lecture, by Sir Arthur Eddington, on 'The Expanding Universe'. Most of the small European countries were represented by two or three delegates only, but the delegations of France and Great Britain were composed of 20 and 18 scientists respectively; at that time there were only two delegates from Germany. After the Brighton General Assembly, with about 200 commission meetings - one commission met eleven times! - six Joint Discussions, four Invited Discourses, a Special Meeting and hardly time for excursions, there were a few complaints about too many overlapping meetings.

The many papers by Soviet authors have been translated into English by A. P. Kirillov, N. A. Nikiforova, E. A. Voronov, and others. Some of the papers were trans lated by the authors themselves. The discussion records have been prepared at the Institute for Theoretical Astronomy by V. K. Abalakin, N. A. Belyaev, A. P. Kirillov, V. A. Shor, E. A. Voronov, N. S. Yakhontova, and others. The three papers published in French have been carefully checked by B. Milet. The final editing has been done at the Smithsonian Astrophysical Observatory, and we thank J. H. Clark, P. D. Gregory, J. E. Kervick, and G. Warren for retyping much of the material. Our special thanks are due to the D. Reidel Publishing Company for the excellent care they have taken in printing these proceedings of IAU Symposium No. 45. G. A. CHEBOT AREV E. I. KAZIMIRCHAK-POLONSKA Y A B. G. MARSDEN INTRODUCTION The idea to organize a Symposium on 'The Motion, Evolution of Orbits, and Origin of Comets' dates back to the IAU thirteenth General Assembly, held in 1967 in Prague. Owing to the impossibility of completing during the General Assembly the discussion on the problem of orbital evolution of comets Professor G. A. Chebotarev, then the newly elected President of IAU Commission 20, initiated the organization of the international symposium in Leningrad where the full scope of cometary problems might be considered from the viewpoint of celestial mechanics.

A new frontier in our solar system opened with the discovery of the Kuiper Belt and the extensive population of icy bodies orbiting beyond Neptune. Today the study of all of these bodies, collectively referred to as trans-Neptunian objects, reveals them to be frozen time capsules from the earliest epochs of solar system formation. This new volume in the Space Science Series, with one hundred contributing authors, offers the most detailed and up-to-date picture of our solar systemÕs farthest frontier. Our understanding of trans-Neptunian objects is rapidly evolving and currently constitutes one of the most active research fields in planetary sciences. The Solar System Beyond Neptune brings the reader to the forefront of our current understanding and points the way to further advancement in the field, making it an indispensable resource for researchers and students in planetary science.