The present report covers the period 1979-1981. As with previous reports it has not been possible to write an all-inclusive account covering everything published, or even every field under investigation; the number of contributions to extragalactic research is increasing faster every year. Summaries of the papers may be found in the Astronomy and Astrophysics Abstracts.

During the interval covered by this report, Commission 29 has sponsored or cosponsored the following IAU meetings: Symposium 98 on “Be Stars,” Munich, FRG, April 1981; Colloquium 59, “Effects of Mass-Loss on Stellar Evolution,” Trieste, Italy, September 1980; and Colloquim 70, “The Nature of Symbiotic Stars,” Haute-Provence, France, August 1981. In addition, Commission 29, through its Working Group on Ap Stars, collaborated in the organization of the 23rd Liege International Astrophysical Symposium on Upper Main-Sequence Chemically Peculiar Stars. Several IAU symposia and colloquia proposed for 1982 and 1983 are also cosponsored by Commission 29.

This report reviews briefly the works achieved or planned in the triennium from 1979 to 1981 on the subjects to be considered by Commission 31. Reports of contributions furnished kindly from different institutions by many of Commission members were obliged to be partly omitted or abbreviated owing to the limitation of space, for which hearty thanks and apologies as well are to be given.

Astronomical observations for UTO-UTC have been continued on a routine basis in participating observatories to BIH with PZT's, astrolabes, transit instruments etc. The observations with 35-km interferometer have been made by USNO, and are expected to contribute an important part to future efforts.

According to Commission 33 traditions, the report contains contributions from a number of authors: K2 , D.L. Crawford, §3, W.B. Burton and F.J. Kerr, §4, W.B. Burton, §5, K. Loden, §6 A and C, R. Wielen, f-6 B, U. Haud and J. Einasto, §6 D and §7, D. Lynden-Bel], §6 E and F, M. Fujimoto.

The subject of interstellar matter continues to be one of the most active fields of present day astronomical research. The advent of new instruments operating in the different parts of the electromagnetic spectrum has resulted in a phenomenal increase both in the amount of observational material, and in the theoretical work attempting to interpret or model the observations. This has made it increasingly difficult to cite all of the published work in the field, and to have room to report even in brief on the conclusions of these studies.

Once again this report consists of detailed discussions of a limited number of topics of current interest, which have not been discussed in recent reports. The subjects are: Mixing in Stellar Evolution (A. Maeder); Supernovae (J. Craig Wheeler); Theory of Variable Stars (J. Cox); Theoretical Studies of Star Formation (J. J. Monaghan); The Age and Helium Content of Globular Clusters (V. Castellani). Because the first three contributions have been written by different authors there is a small amount of overlap in their contents. I am very grateful to the authors for providing their reports very promptly. The references are in general identified by their number in Astronomy and Astrophysics Abstracts but many references are too recent for this to be possible and a few others were not included in A & A Abstracts.

Commission 36 acts as a cosponsor of the following Symposia: (1) IAU Symposium No. 102 “Solar and Stellar Magnetic Fields: Origin and Coronal Effects” Zurich, Switzerland (2-6 August 1982) and (2) IAU Symposium No. 103 “Planetary Nebulae” London, UK (10-1U August 1982). The commission participates jointly with Commissions 29, 35, and 45 in the organization of a Joint Discussion at the IXth General Assembly on the topic “Mass-Loss-Phenomena”.

The past triennium has been a very active period in most branches of cluster research. Some controversial subjects, notably globular cluster abundances and ages have received much attention. A good number of photometric papers on clusters as well as associations have been published. Observational effects of mass loss have been discussed by several astronomers.

This report has been assembled by the president of the commission although several sections have been contributed by other members. The report will first list some highlights in the activities of our commission. Then follow the tables containing current investigations of OB associations, open clusters and globular clusters. These have been assembled by B. Balázs, G. Harris and R. White, respectively. After these tables comes a section by D. Heggie about dynamics of star clusters. A working group under the chairmanship of A. Moffat has made a proposal about the numbering of stars in clusters. The proposal, which is included here will be discussed by our commission at the IAU General Assembly.

This report covers surveys of radio sources, basic measurements of source parameters and new developments in radio telescopes, instrumental techniques and data processing. The period covered is approximately late 1978 to about August 1981. The results and conclusions of astronomical investigations based on measurements made through the radio window are included in the reports of other commissions, as relevant. Following the practice adopted in 1979, a circular was sent to the Presidents of 18 IAU Commissions and to all members of Commission 40 describing the proposed format of the present report and also identifying contact persons who could be consulted to avoid duplication and to ensure that radio astronomical results are adequately covered by various commissions. I am grateful to all concerned for providing the necessary coordination.

Interest in close binary stars continues to grow apace. Substantial fractions of the observing time on the International Ultraviolet Explorer and the various X-ray satellites have been devoted to extending our knowledge of a variety of interacting binaries. These, together with applications of novel ground-based techniques and the steady improvement of traditional methods, and developments in methods of analysis, have led to major advances in understanding of the properties and evolution of close binary stars.

Our Symposium Close Binary Stars held in Toronto, 7-10 August 1979, was attended by 170 participants from 26 countries and over 100 papers were presented. The proceedings have been published as IAU Symposium No. 88, Close Binary Stars: Observations and Interpretation, eds. M. Plavec, D.M. Popper and R.K. Ulrich; Reidel Publishing Co., 1980.

The coming of age of space astronomy is evident from the ever increasing involvement of astronomers with space observatories. In the last years we have witnessed a tremendous growth of papers in the literature on the interpretation of results from space observations. The range of astronomical topics affected by space observations is very wide, covering the gammut from stellar birth to cosmology. Chapters following this brief introductions amply illustrate this encouraging development. Space astronomy is no longer a field exploited only by a few specialists.

The years covered in this report (1979-81) have been active ones in the field of stellar classification, as is made obvious in the following sections. In addition to the individual references listed there, a number of symposia, colloquia, and workshops were held during the report period which included papers relevant to stellar classification. These include IAU Symposia 85 (Starclusters), 98 (Be stars), and 99 (Wolf-Rayet stars); IAU Colloquia 64 (Automated Data Retrieval in Astronomy) and 68 (Astrophysical Parameters for Globular Clusters); and the Dudley Observatory Workshop on Problems of Calibration of Multicolor Photometric Systems (1979).

The projects of this Commission are increasingly aimed at the astronomically developing countries. The projects are:

International Schools for Young Astronomers. These are the highest-priority activity of the Commission. They last three weeks, have typically 25 to 35 participants, cover a range of astronomical topics with emphasis on practical training, and are funded by the IAU, UNESCO, and local sources. This report covers three schools: i) La Laguna, Tenerife, Spain, September 1979, participants from Spain, Portugal, Canary Islands and five Latin American countries, ii) Hvar, SR Croatia, Yugoslavia, September – October 1980, participants from Balkan and Mediterranean countries, iii) Helwan Observatory, Cairo, Egypt, participants from Egypt, Saudi Arabia, Sudan, Nigeria, Tanzania, Greece, Portugal, Hungary, China.

For the preparation of this report, I solicited recommendations from all members of the Commission, and also invited them to submit very brief statements of activities of themselves or others that they believed should be considered for inclusion. I received a large number of replies (unfortunately, many in the form of extensive reprints and preprints). I have tried to incorporate most suggestions, and to summarize the activities of Commission members as well as activities described in other sources to provide as broad an account as I have been able of the developments relating to cosmology since the last General Assembly in 1979. In am sure, however, that this report falls short of being complete, especially in the areas of theoretical cosmology, in which I am not really expert.

This commission is intended to study the following problems: (1) the solar corona, i.e. the region of the origin of the solar wind; (2) the heliosphere, i.e. the region dominated by the supersonic solar wind as it expands through the neutral component of the interstellar medium; (3) the heliospheric interface, i.e. the region in which the interaction between the two counterstreaming magnetized plasmas, the subsonic solar wind and the interstellar medium, takes place. The activities of this commission cover both theoretical and observational investigations of these three regions.