Bøger af Zdenek Kopal

ASTRONOMICAL ECLIPSE PHENOMENA In looking over the long history of human science from time immemorial to our own times, it is impossible to overestimate the role played in it by the phenomena of eclipses of the celestial bodies-both within our solar system as well as in the stellar universe at large. Not later than in the 4th century B. C. , the observed features of the shadow cast on the Moon by the Earth during eclipses led Aristotle (384-322 B. C. ) to formulate the first scientific proof worthy of that name of the spherical shape of the Earth; and only somewhat later, the eclipses of the Sun provided Aristarchos (in the early part of the 3rd century B. C. ) or Hipparchos (2nd half ofthe same century) with the geometric means to ascertain the distance which separates the Earth from the Sun. In the 17th century A. D. (in 1676, to be exact) the timings of the eclipses of the satellites of Jupiter by their central planet enabled Olaf Romer to discover that the velocity with which light propagates through space is finite.

The words of this preface were written when the book was ready to go to the press; and are limited to only a few points which are best made in this place. As is intimated by the sub-title, the whole volume was written with appli­ cations in mind to double-star astronomy. The latter is, however, not the only branch of our science which could benefit from its contents. The same is true of certain aspects of the dynamics of stellar systems or galaxies (the stellar popula­ tions of which are also characterized by the fact that the mean-free-path of their constituent stars are long in comparison with the dimensions of the respective systems); the central condensations of which are high enough to approximate the gravitational action of a "mass-point". This fact did not, to be sure, escape the attention of previous investigators (in the case of globular clusters, in particular, the Roche model was introduced in their studies under the guise of polytropic models characterized by the index n = 5); though no particular attention will be paid to these in this book. But possible applications of the Roche model are not limited to problems arising in stellar astrophysics. With Coulomb forces replacing gravitation, the equilibrium model finds a close analogy in the field of electrostatics-as was pointed out already at the beginning of this century by (then young) J. H. Jeans (cf.

If Zdenek Kopal Department of Astronomy University of Manchester Your Magnificences, my Lord Mayor, ladies and gentlemen! It is a great pleasure for me to respond, on behalf of your foreign guests, to your gracious words of welcome; and to thank you for the wonderful reception which you nave extended to us. The city of Bamberg and its Remeis Sternwarte nas indeed been renowned allover the world for a great many years - as the place where your Observatory's first director, Professor Ernst Hartwig (1851-1923) - in addition to his other titles to fame - collaborated (with Gustav Muller of Potsdam) on the construc­ tion of the monumental Geschichte und Literatur des Lirhtwechsels der Veranderlichen Sterne, which since 1918 has (together with its sub­ sequent continuation) been a veritable vade-mecum of a1l students of variable stars; where the second director, Professor Ernst Zinner (1886-19]~ prepared his valuable Katalog der Verdachtigen Veranderlichen Sterne (192@ which safeguarded many an astronomer (including the present speaker in the days of his innocence) from premature discovery claims; and whose third director, Professor Wolfgang Strohmeier, initiated in 1959 the tradition of the international colloquia of which ours is the latest successor. It is indeed a great pleasure to welcome Professor Strohmeier - now Emeritus - among us; and to congratulate him on the grace with which he is carrying his years.

The aim of the present book will be to provide a comprehensive account of our present knowledge of the theory of dynamical phenomena exhibited by elose binary systems; and on the basis of such phenomena as have been attested by available observations to outline probable evolutionary trends of such systems in the course of time. The evolution of the stars - motivated by nuelear as weIl as gravitation al energy sources - constitutes nowadays a well-established branch of stellar astronomy. No theo­ ries of such an evolution are as yet sufficently specific - let alone infallible - not to require continual tests by a confrontation of their consequences with the observed prop­ erties of actual stars at different stages of their evolution. The discriminating power of such tests depends, of course, on the range of information offered by the test objects. Single stars which move alone in space are now known to represent only a minority of objects constituting our Galaxy (cf. Chapter 1-2); and are, moreover, not very revealing of their basic physical characteristics - such as their masses or absolute dimensions. If there were no binary systems in the sky, the only star whose vital statistics would be fully known to us would be our Sun.

After several decades spent in astronomical semi-obscurity, the Moon has of late suddenly emerged as an object of considerable interest to students of astronomy as well as of other branches of natural science and technology;

ASTRONOMICAL ECLIPSE PHENOMENA In looking over the long history of human science from time immemorial to our own times, it is impossible to overestimate the role played in it by the phenomena of eclipses of the celestial bodies-both within our solar system as well as in the stellar universe at large.

A favourable reception of the first edition of this book - due no doubt to the nature of its subject - which went out of print in 2 years, gave its author a welcome oppor tunity to update at present its contents.

The aim of the present book has been to provide an outline - the first of its kin- of the history of the human efforts to map the topography of the surface of our satellite, from the days of pre-telescopic astronomy up to the present.

The aim of the present book will be to summarize the results of the space exploration of the Moon in the past fifteen years -culminating in the manned Apollo missions of 1969-1972 -on the background of our previous acquaintance with our satellite made in the past by astronomical observations at a distance.

No theo ries of such an evolution are as yet sufficently specific - let alone infallible - not to require continual tests by a confrontation of their consequences with the observed prop erties of actual stars at different stages of their evolution.

The twentieth century has been a remarkable epoch in the affairs of men, and this is no less true of astronomy, at once the oldest and most modern of the sciences. Sky watchers at the beginning of the century measured positions and predicted celestial motions in faithful but uninspired homage to the Muse Urania; nowadays, their descendents call on all the resources of modern science to probe the nature and evolution of a bewildering range of celestial objects. Man has even set out to call personally on his nearest neighbours in space. Professor Zdenek Kopal has lived and practised astronomy throughout this efflorescence of his subject. Born in Czechoslovakia just before the outbreak of the Great War, and educated in the classical European tradition, he knows well the days when scholars commanded such respect that astronomical congresses would be visited by Heads of State. Yet within his own lifetime, he has himself been recruited to play an important role in scientific preparations for a manned Moon landing. He has known and worked with some of the most highly respected practitioners of Modern Astromomy: Russell, Shapley, Urey in the United States, Eddington in Britain. His fine eye for detail, coupled with his strong sense of history, enable him to unfold through his personal recollections the development of his subject across the social changes of two world wars. Inspired by his grandfather, who would think nothing of walking sixty miles to theatrical performance, the young Kopal acquired a Wanderlust that has taken him in his career more than a dozen times rond the world. He has visited the most ancient observatories, observed solar eclipses in Japan and Java, helped to establish new institutions in Iraq and India, and commuted for many years between the Old and New Worlds. He has toiled in every corner of his chosen vinyard: as observer, outstanding theoretician, populariser, editor and teacher. During his thirty years as Professor of Astronomy at Manchester, he helped to educate over a hundered PhD students, many from the developing world, who have taken the torch of astronomy back to their home lands. In retirement, he continues to direct his efforts towards a better understanding of the Universe, and shows no sign of abandoning his life-long affair with the heavens. Professor Kopal has entitled his book Of Stars and Men, for he has delighted in the company of both throughout his life. The reader is invited to share with him the story of his birth, his education, his work and his travels; and to join with him in contemplating the history and possible future of his subject, and of civilisation itself.

Eclipsing Variables - What They can Tell Us and What We can do with Them The aim of the present book will be to provide an introduction to the inter pretation of the observed light changes of eclipsing binary stars and their analysis for the elements of the respective systems.