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Proceedings of the Thirteenth General Assembly, Prague 1967

This written account of the Symposium on Planetary Nebulae was prepared from manuscripts submitted by the participants. Nearly every paper that was presented at the meeting is reproduced here, in either complete or abbreviated form. The dis­ cussions have been somewhat shortened and rearranged, but we have tried to preserve the essential points and the general tenor of the exchanges. Participants who spoke in the discussion were asked immediately for written remarks, which were then edited, reproduced, and circulated at the meeting by the highly effective local Secretariat organized by Dr Perek. In addition, notes of the discussion taken by Mrs Edith F. Swan and by the undersigned were used. We wish to thank all the authors for their unusually good cooperation. We are especially grateful to Dr Minkowski, who kindly provided many excellent repro­ ductions of Mount Wilson and Palomar photographs, mostly taken by himself, of various planetary nebulae. We are particularly indebted to Mrs Swan, who attended the Symposium, made notes on the papers and discussions as they occurred, and did much of the checking and editing of the manuscripts. In addition, we are very grateful to Mrs Evelyn Seaver, who also did much of the checking, editing, and retyping of manuscripts, and to Dr B.L. Webster, Miss Rebecca Todd, Mr Joseph Tapscott, and Mr Dennis Schatz, who provided excellent assistance in the preparation of this volume.

The idea of the organization of a Symposium on Spiral Structure came at a special meeting of Commission 33 on Spiral Structure during the 12th General Assembly of the IAU in Prague, 1967. So much interest was shown during this meeting that one of us proposed a special Symposium on the 'Spiral Structure of Our Galaxy' for 1969. The response was immediate and it was finally agreed upon holding the Symposium in Basel, a center of galactic research in the center of Europe. During the next months a special 'List of Problems', related to this Symposium, was sent to many prospective participants by the president of Commission 33. This stimulated an increase of interest in problems of galactic spiral structure and a con­ centrated effort on some problems. The organizing Committee of the Symposium was composed of Drs. L. Woltjer (president), W. Becker, A. Blaauw, B. J. Bok, G. Contopoulos, F. J. Kerr, C. C. Lin, S. W. McCuskey and S. B. Pikel'ner. Most of the work for the organization of the Symposium was carried by Dr. L. W oltjer. The Local Committee, composed of Drs. W. Becker, U. W. Steinlin, R. P. Fenkart, and G. A. Tammann, made every effort to secure the success of the Symposium. Most of the credit goes to Dr. Steinlin. The Symposium was supported financially by the IAU and by the Swiss National Science Foundation. The meetings took place at the University of Basel, which provided also secretarial help and many other facilities.

IA U Symposium Number 141 "Inertial Coordinate System on the Sky" was held in Leningrad, USSR from 17-21 October 1989. The symposium also commemorated the 150th anniversary of the founding of Pulkovo Observatory. The scientific program was presented in ten half-day sessions. Most sessions were held at the Pulkovskaya Hotel, but one session which highlighted Pulkovo's current programs was held at Pulkovo Observatory. The sessions were organized into general categories pertaining to the legacy of Pulkovo for inertial systems; current programs at Pulkovo Observatory; concepts, definitions and models; and the realization and comparision of reference frames. More than 140 scientific papers were presented, either orally or in poster form. Extensive use was made of electronic mail and computer-readable communications, and more than two-thirds of the authors made use of the opportunity to submit papers for formatting by the editors. The meeting was truly a symposium in the Greek sense of the word-a free-flowing exchange of ideas and opinions. The final two papers presented at the symposium by Wilkins and by Westerhout are presented at an eady stage in the published proceedings, in order to help focus the reader's attention on the concepts and problems explored in subsequent papers. As pointed out by G.

H.T. MacGilLIVRAY Royal Observatory Blackford Hill Edinburgh EH9 3HJ Scotland U.K. lAU Symposium No. 161 on 'Astronomy from Wide-Field Imaging', held in Potsdam, Germany, during 23-27th August 1993, was the first conference organised by the recently-formed Working Group of lAU Commission 9 on 'Wide-Field Imaging'. This Working Group was instigated during the XXIst meeting of the General Assembly of the International Astronomical Union in Buenos Aires in 1991, and represented a merging of the former formal lAU Working Group on 'Astronomical Photography' and the informal 'Digitised Optical Sky Surveys' Working Group. Dr. Richard West was 'invited' to be Chairperson, and hence was given the daunting task of organising the Group from scratch. The very fact that the first conference after only two years was a major lAU Symposium says much about the determination and enthusiasm of Richard West to fulfilling the aims of the new Working Group. The siting of the conference in Potsdam in formerly East Germany provided an excellent opportunity to advantage from the political changes in Eastern Europe. Good access to the meeting was possible by scientists from Eastern European countries, allowing exchange of information on the very important Wide-Field facilities in both East and West, information on the rich archives of photographic plates that exist in both East and West, and allowing discussions between scientists facing very similar problems in both East and West.

The XXth meeting of the IAU in Australia in 1973 made the venue for the IAU Symposium No. 59 on Stellar Instability and Evolution, at Mount Stromlo Obser­ vatory on August 16-18, a very appropriate one. Many of the current and former staff of Mount Stromlo Observatory (operated by the Australian National Univer­ sity) have specialized in the study of variable stars and it was with considerable pleasure that Mount Stromlo Observatory accepted the responsibility of hosting and making the local arrangements for IAU Symposium No. 59. The Scientific Organizing Committee was particularly active in formulating the program and comprised Drs N. Baker, P. Demarque, M. Feast, G. Herbig, I. Iben, P. Ledoux, J. Ostriker and E. Schatzman. The aim of the Committee was to integrate the review and contributed papers on the particular instability mechanisms involved, their observational manifestations and their relation to the internal structure of the star as inferred from its evolutionary history. The Local Organizing Committee consisted of Miss P. Petrie and A. W. Rodgers.

The year 1973 marked the highest peak of IAU activity up to now. Besides the Gen­ eral Assembly in Sydney, and the Extraordinary General Assembly in Poland, there were held eleven IAU Symposia and one Colloquium. Several IAU Publications cover this activity. The Proceedings of the Symposia are published in separate Volumes, while the Transactions of the General Assembly and of the Extraordinary General Assembly contain short reports of the Commission meetings, the administrative sessions, and the opening ceremonies. The present Volume covers some of the scientific Highlights of the General As­ sembly and of the Extraordinary General Assembly. It contains five Invited Dis­ courses given in Sydney and Poland, some selected papers, and the Joint Discussions at the General Assembly of Sydney. Of course, there were many more papers of special interest presented in Sydney that could not be included in this Volume. Their titles can be seen in the reports of the various Commissions. It is regrettable that the Invited Discourses of C. H. Townes (Interstellar Molecules) and F. J. Low (Infrared Astronomy) were not submitted for publication. Also only five papers or abstracts of the Joint Discussion on the 'Origins of the Moon and Satellites' have been available. Despite these minor shortcomings, I believe that the present Volume is faithful to its title: it gives a substantial part of the Highlights of Astronomy in 1973.

IAU Symposium Number 52 on Interstellar Dust and Related Topics was held at Albany, N.Y., on the campus of the State University of New York at Albany from May 29 to June 2, 1972. The members of the Organizing Committee were: Dr A. D. Code, University of Wisconsin, Madison, Wis., U.S.A. Dr B. D. Donn, Goddard Space Flight Center, Greenbelt, Md., U.S.A. Dr A. Elvius, Stockholm Observatory, Saltsjobaden, Sweden. Dr T. Gehrels, Lunar and Planetary Laboratory, University of Arizona, Tucson, Ariz., U.S.A. Dr J. M. Greenberg (Chairman), State University of New York at Albany, Albany, N.Y., U.S.A. Dr H. C. van de Hulst, Sterrewacht, Leiden, Holland. Dr S. B. Pikel'ner, Sternberg Astronomical Institute, Moscow, U.S.S.R. Dr E. E. Sal peter, Cornell University, Ithaca, N.Y., U.S.A. Dr B. E. Turner, National Radio Astronomy Observatory, Charlottesville, Va., U.S.A. The suggestion was first made in 1971 that a symposium on interstellar grains would be timely. The response to the first preliminary announcement, which was sent out on November 29, 1971, was well beyond our expectations. The meeting was locally sponsored by the State University and by Dudley Observatory. The National Aeronautics and Space Administration and the National Science Foundation con­ tributed along with the JAU. There were 158 participants of whom 49 were from 15 countries outside the United States. A total of 92 papers were presented.

The galactic and extragalactic background radiation components are of major importance in astrophysical studies of a variety of problems related to galactic structure, interstellar matter, the distribution and evolution of galaxies and intergalactic matter, and cosmology. The back­ ground radiation is a unique source of information in cases where the source is of a truly diffuse nature, as with scattering and emission by interstellar dust and gas, or where the discrete emission sources are so faint (e. g. , very distant galaxies) that they can be observed only by their integrated emission. The galactic and extragalactic background must be discussed together because they are observationally entangled and their proper separation requires a knowledge of both components. The above points are equally valid for the entire electromag­ netic spectrum, from gamma rays to long radio waves. Thus, the study of the galactic and extragalactic background radiation is interdisciplinary in its character, and a multi wavelength approach would appear to be dictated by the nature of the topic. The proper separation of the galactic and extragalactic background components requires a knowledge of both. In addition, the foreground components, i. e. , zodiacal light, airglow, and atmospheric scattered light, must be treated carefully.

Our first attempt to organize a Symposium on solar activity was made at the lAO General Assembly in Brighton 1970. There, at the session of Commission 10, we proposed to organize a Symposium which would stress the observational aspects of solar activity. It was our hope that such a Symposium might stimulate studies of those important problems in solar physics which for a long time had been neglected in overall scientific discussion. Although a provisional date for the Symposium was then decided, it did not take place to avoid overlapping with other lAO activities. At the session of Commission 10 in Sydney -on the occasion of the XVth lAO General Assembly in 1973 -we repeated our proposal and forwarded the invitation of the Czechoslovak Academy of Sciences to organize the Symposium in Prague. Both were accepted. During the discussions about the programme of the Symposium -enthusiastically promoted by the late president of Commission 10, Prof. K. O. Kiepenheuer -it was decided to change slightly its subject. The theoreti­ cal problems were stressed and the majority of the Scientific Organizing Committee agreed not to deal with short-lived phenomena of the solar activity or with individual active regions. Symposium No. 71 was held in Prague from August 25 to August 29, 1975. Its Organizing Committee consisted of V. Bumba (Chairman), W. Deinzer, R. G. Giovanelli, R. Howard, K. O. Kiepenheuer, M. Kopecky, T. Krause, M. Kuperus, G.

Proceedings of the 132nd Symposium of the International Astronomical Union, held in Paris, France, June 29-July 3, 1987

The cosmic radiation was discovered by Hess in 1912 but its origin is still the subject of much controversy and considerable study. For several decades most workers in the cosmic ray field were interested in the Nuclear Physical aspect of the particle beam and many important dis­ coveries were made, notably the identification of the positron, the muon, the pion and the strange particles. More recently however, em­ phasis has changed to the Astrophysical aspect both with re8ard to the origin of the radiation and to its relation with the other radiation fields. Mindful of the increasing importance of the Astrophysical facets of the subject the Cosmic Ray Commission of IUPAP approached the High Energy Astrophysics Commission of the IAU with the suggestion of a joint Symposium on Cosmic Ray Origin. The plan was to bring together workers in all the various astronomical fields - from Radio, through Optical to Gamma Rays - with Cosmic Ray physicists and to fully explore the various interrelations. The approach was received with enthusiasm and this book contains the proceedings of the ensuing Symposium, (styled IUPAP/ IAU Symposium No. 94) which was held in Bologna from 11th - 14th June 1980. Virtually all the papers presented are reproduced here. The Scientific Organizing Committee chose the invited speakers whose papers formed the major scientific component of the meeting. Additional short contributed papers were also called for and very brief 2-page resumes (which have not been refereed) are given in the proceedings.

The General Assemblies of the International Astronomical Union are landmarks in the life of the world-wide astronomical community, as they review, at triennial intervals, the progress made in this scientific field, promulgate the most spect­ acular astronomical achievements, formulate scientific programmes for the years to come and, last but not least, deal with the administration and finances of the IAU. The Reports on Astronomy 1976, published as Transactions XVIA (in 3 volumes) before the XVlth General Assembly, are a synopsis of the work done in astronomy from 1973 to 1975. The volume "Highlights of Astronomy , as presented at the XVlth General As­ sembly of the IAU in Grenoble, 1976" includes some selected scientific topics, and will appear in the first half of 1977. Apart from the Invited Discourses and the Proceedings of the seven Joint Discussions, the Highlights volume No.4 con­ tairsthe proceedings of two Joint Commissions Meetings.

The symposium on 'Solar Gamma-, X- and EUV Radiation' was held at Buenos Aires, Argentina, from 11 June to 14 June 1974. It was sponsored jointly by the Inter­ national Astronomical Union (IAU) and the Committee on Space Research (COSPAR). The Organization Committee responsible for the program consisted of Drs K. A. Anderson (Chairman), J. L. Culhane, G. Elwert, B. B. Fossi, S. L. Mandel­ s'tam, W. M. Neupert, V. K. Prokofiev, and J. Sahade and representatives of COSPAR, Drs H. Friedman and Z. Svestka. During the symposium Dr Svestka kindly represented the chairman of the Organizing Committee who was unable to attend the symposium. The local arrangements in Buenos Aires were made by Drs J. Sahade (Chairman), H. S. Ghielmetti, M. J. Gulich, H. Molnar, J. J. Tasso and N. Martinez Riva de Tropper. This symposium brought together the observational and theoretical aspects of the Solar Gamma-, X-, and EUV Radiation and other related solar emissions such as radio and energetic particles. There were three specific topics for the symposium, viz.

Proceedings of IAU Symposium No. 58 held in Canberra, Australia, August 12-15, 1973

The Symposium on the Crab Nebula was held in the University of Manchester from 5 to 7 August, 1970. The meetings on the first day were held in the Physics Department on the University campus, and on the second and third days at the Nuffield Radio Astronomy Laboratories, Jodrell Bank. The 4th Symposium of the International Astronomical Union, convened in the University and at Jodrell Bank fifteen years earlier (25-27 August, 1955), dealt with the entire subject of radio and radar astronomy. Now the subject matter of this 46th Symposium of the International Astronomical Union was confined to one single object. It is interesting to recall that even at the 1955 symposium the Crab Nebula figured prominently. In particular, J. H. Oort described the new measurements of the polariza­ tion of the light from the nebula and I. S. Shklovsky explained the light and radio emission in terms of the motion of relativistic electrons in the magnetic field of the nebula. No one could have foreseen the exciting discoveries of a decade later which stimulated the assembly of 172 participants to this 1970 Symposium. In addition to the lectures and discussions the visitors were able to tour the laboratories and telescopes at J odrell Bank to see the various researches in progress. The demonstrations included a real-time display on a cathode ray tube of the pulses from pulsar CP 0328 received in the 250 ft steerable telescope.

When the Executive Committee of the International Astronomical Union asked me, in 1968, to organize a Symposium on White Dwarfs it became evident that members of at least four Commissions of the IAU should participate, and that the most oppor­ tune place, and time to hold such a Symposium would be somewhere in the British Isles and just preceding the Fourteenth General Assembly at Brighton in August, 1970. After a preliminary correspondence with Dr. D. W. N. Stibbs it was decided to accept his invitation to hold the Symposium at St. Andrews University, Scotland, while the dates 11-13 August 1970 were selected. I am sure I speak for all the partici­ pants of the Symposium when I express our deep gratitude to Dr. Stibbs for the admirable way in which he planned and organized this meeting down to the smallest details - the success of the conference is due in no small measure to his continuous and painstaking efforts. An organizing committee was formed, consisting of O. J. Eggen (Photometry), J. L. Greenstein (Spectroscopy), A. G. Masevitch (Stellar Interiors), V. Weidemann (Stellar Atmospheres), D. W. N. Stibbs (local chairman), with myself (Proper Motions and Parallaxes) as overall chairman.

Solar and stellar photospheres constitute the layers most accessible to observations, forming the interface between the interior and the outside of the stars. The solar atmosphere is a rich physics laboratory, in which the whole spectrum of radiative, dynamical, and magnetic processes that tranfer energy into space can be observed. As the fundamental processes take place on very small spatial scales, we need high· resolution observations to explore them. On the other hand the small-scale processes act together to form global properties of the sun, which have their origins in the solar interior. The rapid advances in observational techniques and theoreticallllodelling over the past decade made it very timely to bring together scientists from east and west to the first lAU Symposium on this topic. The physics of the photosphere involves complicated interactions between magnetic fields, convection, waves, and radiation. During the past decade our understanding of these gener­ ally small-scale structures and processes has been dramatically advanced. New instrumen­ tations, on ground and in space, have given us new means to study the granular convection. Diagnostic methods in Stokes polarimetry have allowed us to go beyond the limitations of spatial resolution to explore the structure and dynamics of the subarcsec magnetic struc­ tures. Extensive numerical simulations of the interaction between convection and magnetic fields using powerful supercomputers are providing deepened physical insight. Granulation, magnetic fields, and dynamo processes are being explored in the photospheres of other stars, guided by our improved understanding of the solar photosphere.

It is the customary practice to report the major events of a General Assembly -the Invited Discourses, Joint Discussions and Joint Commission Meetings in Highlights of Astronomy. Vol. 8 reports the highlights of the XXth General Assembly of the International Astronomical Union, 1988 August 2-11, Baltimore, USA. The present volume contains the 3 Invited Discourses and papers presented at 7 Joint Discussion Meetings and 6 Joint Commission Meetings. Two Joint Commission Meetings will be reported elsewhere -JCM5 Spectroscopy of Individual Stars in Globular Clusters and the Early Chemical Evolution of our Galaxy (in summary only here, published by the Imprimerie de l'Observatoire de Paris) and JCM7 Star Clusters in the Magellanic Clouds (see Transactions of the IAU, Vol.XXB, report of Commission 37). I am most grateful to the authors of the invited discourses R.M. West and V.I. Moroz, M. Schmidt and M. Rees for sending me the manuscripts so promptly. I am also indebted to the Chairmen of the Joint Discussion and Joint Commission Meetings for their organisation of the meetings and for the assembly of their material for publication. Unfortunately the deadline for receipt of manuscripts coincided with an extended postal strike in France which seriously hindered the preparation of the volume for publication.