The last three years have been very productive for cluster research, especially now that observations with CCDs have become so routine. After a section on recent meetings, and one on data catalogues (by J.-C. Mermilliod), subsequent sections of this report go into details on individual topics: associations (P.E. Nissen), open clusters (G.L.H. Harris), globular clusters and cluster systems (R.E. White) and dynamical theory (D.C. Heggie).

The rapid growth in the volume of observational data has meant regrettably that the information has had to be tabulated in an even more compressed form than in earlier Reports. As in previous Reports, three-figure references are to Astronomy and Astrophysics Abstracts, and two-figure references to Physics Abstracts. Most entries cover publications from 1 July 1984 to 30 June 1987, but some exceptions are noted under the individual sections. For abbreviations see §6.

The present report covers the period 1 February 1985 to 30 November 1987. During this period a total of 23 travel grants were awarded as follows:

The following commission members have contributed to this report:

M Birkinshaw, R J Cohen, J J Condon, T J Cornwell, J R Dickel, P A Feldman, R Genzel, M Goss, V Kapahl, Gopal Krishna, M Kundu, A G Lyne, C R Masson, A C Readhead, W Reich, J M Riley, A J Turtle, J M van der Hulst, T L Wilson.

Commission 41 has been involved in one colloquium and one symposium since the last report:

IAU Colloquium 91 on “The History of Oriental Astronomy” was held in New Delhi, November 13-16, 1985, preceding the XlXth General Assembly. Members of the scientific organizing committee were S.M.R. Ansari, E.S. Kennedy, D. King, R. Mercier, O. Pedersen, D. Pingree, G. Saliba, Xi Ze-Zong and K. Yabuuti. The colloquium was co-sponsored by the International Union for the History and Philosophy of Science, and by a number of organizations in India: the Council of Scientific and Industrial Research, New Delhi, the Department of Science and Technology, New Delhi, the Indian Institute of Astrophysics, Bangalore, the Indian National Science Academy, New Delhi, the Tata Institute of Fundamental Research, Bombay, and the University Grants Commission, New Delhi. The local organizing committee, chaired by G. Swarup, made possible a number of local excursions, including a conducted tour of the great stone open air observatory, built in the city by the enlightened Maharadjah Jai Singh in the 18th century. The colloquium brought 84 participants from 19 countries. 46 papers were presented of which 10 were invited, covering aspects of astronomy in the far east and middle east since the earliest civilizations. Papers from Colloquium 91 have now been published in book form: History of Oriental Astronomy, G. Swarup, A.K. Bag, and K.S. Shukla, editors, Cambridge University Press, Cambridge, England, 1987. Contributions are divided into three broad categories: ancient astronomy and its characteristics, ancient elements and planetary models, and medieval astronomy. Within these are papers on the characteristics and achievements of early astronomy in the eastern half of the world, including inter-regional development and mutual influences, ancient data relating to eclipses, supernovae and comets, medieval astronomical developments, instruments and early observatories, and the interplay between observational and theoretical astronomy. A short introductory paper by the revered historian E.S. Kennedy opens the book, as it set the stage for the colloquium in New Delhi: “We find (astronomy) originating a few centuries before the Christian era in two disparate cultures, Mesopotamia and the Hellenistic world. From the Mediterranean it passed to India, there to flourish. Thence the centroid of activity moved westward, residing in the lands of Islam during medieval times, more recently in Europe. Now astronomical research is carried out throughout the entire world.”

During the XlXth General Assembly of the IAU in Delhi the number of members of Cotrmission 42 increased to 260. This simply reflects the growing interest and importance of our field. Growing is not only the number of astronomers involved in research on CBS but also the number of papers resulting from that activity. As an example one can quote the numbers of papers listed during the last few years in Sections 117 (Close Binaries), 119 (Eelipsing Binaries), and 120 (Spectroscopic Binaries) of the Astronomy and Astrophysics Abstracts: 705(1982), 775(1983), 836(1984), 1080(1985), and 911(1986); note that many additional references could be added to these numbers from other sections. Naturally, such numbers alone do not reflect the quality and even less so the position and significance of the CBS field. Here one could perhaps mention an impressive record of successful research proposals involving requests for the observing time on large, ground based telescopes and on space instruments. Indeed, in spite of a very strong competition from other fields, programs involving CBS are usually placed very high on the priority lists (cf. Sections 2D and 2E). Obviously, the close binary systems, their evolution, and the physical processes which occur in them (accretion, stellar winds, nuclear burning, etc) appear interesting and important not only to those who are involved in their studies but also to astronomers from other fields.

The tragic loss of Space Shuttle Challenger and her 7 crew members in January 1986 has seriously affected the astronomical research from space in the U.S.A. and, to a lesser extent, in Western Europe. The incident has caused setbacks in a number of space projects, including the delay in the launching of the Hubble Space Telescope. Nevertheless, the field of space astronomy remained active during the present reporting period (1984 July through 1987 June).

X-ray astronomy has continued to flourish in the three years covered by the present report (to June 1987) despite the continuing scarcity of new missions. The European EXOSAT has probably made the greatest impact during this period, carrying out over 2000 separate observations up to it’s loss of attitude control in April 1986. A major reason for the success of EXOSAT was the unusual spacecraft orbit which provided uniquely long source exposures, uninterrupted by Earth occultation, of up to 70 hours duration. The continuous light curves of many galactic and extragalactic sources have proved particularly valuable in studying details of time variability over a broad frequency range and in this respect the EXOSAT data archive is unlikely to be superceded in this century. For several months after the demise of EXOSAT, astronomers had no operational X-ray satellite for the first time since the launch of Uhuru in 1970. This unfortunate state of affairs ended in February 1987 with the successful launch of the Japanese ASTRO-C satellite. Three months later, observations began with several X-ray instruments on board the Soviet MIR space station and at the time of writing both GINGA (the post-launch name of ASTRO-C) and the MIR instruments are working well.

Results from the IUE satellite, summarized in the section which follows this one, continue to dominate the literature for research topics which rely on observations in the ultraviolet. This trend may be accentuated in the near future, as we experience the natural attrition of papers based on results from previous major missions which are no longer operating, such as TD-1, Copernicus, ANS and BUSS. The Challenger accident on January 28, 1986 abruptly halted flights of new orbital facilities which depend on the Space Shuttle and has created long and somewhat indefinite postponements in the eventual manifesting of payloads ranging in size from simple experiments in Getaway Special (GAS) and Spartan carriers, to telescopes of intermediate size on Spacelab (such as those which were to fly on the Astro mission in March 1986) to the Hubble Space Telescope. Suborbital missions, i.e., sounding-rockets and balloons, will probably dominate the extra-IUE uv astronomy scene until there is a re-establishment of a vigorous launch schedule for expendable vehicles and/or the Space Shuttle.

The period from 1984 through 1987 saw no new infrared space missions. Investigations, however, continued with airborne, balloon, and rocket activities, and follow-up analysis of data from the Infrared Astronomical Satellite (IRAS). Two major ephemeral events occurred during this time, the Comet Halley apparition and SN 1987a, the supernova in the Large Magellanic Cloud. With improved analysis on the database and follow-up observations new results have been forthcoming from IRAS. This work may help astronomers understand everything from the origin and evolution of quasars to the composition of material in cometary nuclei.

Radioastronomy can use space technology either to go close to the source of the radioemission to increase the sensitivity of the observations and have different viewing geometry, or to avoid the effect of the Earth’s environment, i.e. to extend the useful frequency range below the ionospheric cut-off of a few megahertz and at submillimeter wavelengths. A third field which will certainly develop in the future is the use of space to increase the spatial resolution of radio-interferometry for imaging radiosources.

The program of exploration of solar system objects from space is now In a more mature phase where third generation missions to inner as well as outer solar system bodies are developed. Emphasis in the inner solar system is on Mars and Venus, in the outer-solar system on Jupiter (Galileo Mission). The exploration of the primitive small bodies (comets, asteriods) has lagged in the past, partly due to technological considerations. Following the spectacular, but still reconnaissance-level flybys of Comets Giacobini-Zinner and Halley in 1985 and 1986, respectively, ISAS considers a cometary flyby and coma sample return mission, and NASA plans to initiate an even more comprehensive exploration by conducting a close flyby of a main-belt asteroid, followed by a multi-year rendezvous with a short-period comet (CRAF) in the early 1990s.

Stellar Classification is an important activity for astronomers, since it provides “systems” for comparison with new types of stars. A good classification scheme can be used cannily to segregate “peculiar” objects and to gain insight into the processes which generate “normal” objects. Eventually, when there are enough objects in a given “peculiar” class, the definition of “normal” can be extended to include them. Through the process of classification, prototypes can be isolated for detailed study, providing a short-cut to the lengthy process of studying all stars in detail. Thus, classification of stars and maintenance of the reference frames are important.on-going processes in astronomy.

In recognition of increased activity in the subtopics of automatic classification and calibration, they have been assigned separate headings and reporters.

The President is happy to report that a considerable increase of interest in astronomy teaching problems seems to have taken place in many countries during the period 1985-1987. Some countries organized local teachers courses and meetinge, other - national conferences devoted to establishing modern school programmes and training teachers methods including astronomical notions. An international workshop for physics teachers showing possibilities of practical introducing astronomy when teaching physics / GIREP 1986/ brought into contact astronomers and physicists. And, last but not least, teaching problems have been also introduced during the IAU Colloquium No.98, “The Contribution of Amateur Astronomers to Astronomy”, in 1987, while the first IAU meeting dedicated to teaching probleme - the IAU Colloquium No.105 “The Teaching of Astronomy” -is planned for 1988 in Williams town /USA/. Let us hope that in the near future all astronomers will be well aware of their own responsibility in helping astronomical education all over the world.