IAU Commission 19 began in 1919 with the birth of the IAU at the Brussels Conference, where Standing Committee 19 on Latitude Variations was established as one of 32 standing committees. At the first IAU General Assembly in 1922, Standing Committee 19 became Commission 19 “Variation of Latitude”. In the beginning, the main topic of the Commission was the investigation of polar motion. Later, its activities included observations and theory of Earth rotation and connections between Earth orientation variations and geophysical phenomena. As a result, in 1964 at the XII IAU General Assembly, the Commission was renamed “Rotation of the Earth”. The investigation of Earth orientation variations is primarily based on observations of natural and artificial celestial objects. Therefore, maintenance of the international terrestrial and celestial reference frames, as well as the coordinate transformation between the frames and the improvement of the model of precession/nutation, have always been among the primary Commission topics. In 1987, the IAU through Commissions 19 and 31 “Time” established, jointly with the International Union of Geodesy and Geophysics, what is now known as the International Earth Rotation and Reference Systems Service. Commission 19 continued to work to develop methods to improve the accuracy and understanding of Earth orientation variations and related reference systems and frames as well as theoretical studies of Earth rotation. In 2015, Commission 19 was renewed as Commission A2 “Rotation of the Earth” continuing Commission 19’s functions and linking the astronomical community to other scientific organizations such as the International Association of Geodesy, International VLBI Service for Geodesy and Astrometry, International GNSS Service, International Laser Ranging Service and International DORIS Service. During its entire history, IAU Commission 19/A2 has always worked in close cooperation with these and other related services to improve the accuracy and consistency of the Earth orientation parameters and celestial and terrestrial reference frames.

2017 marked the 130th anniversary of the start of the Carte du Ciel project, an ambitious proposal by the Paris Observatory to map the entire sky using photographiy, which required the joint work of numerous observatories in the world. For this endeavour, an impressive organization was designed that included congresses, commissions and publications, which lasted through many years. The Carte du Ciel finally became one of the immediate antecedents of the International Astronomical Union, which in 2019 celebrates its first century. In Latin America, the observatories of Santiago de Chile, La Plata and Rio de Janeiro, the Argentine National Observatory and the Tacubaya Observatory, in Mexico, were involved in the project. In this presentation, we present part of the history of the failures and successes of one of the most important collaborative astronomical projects on the planet.

International scientific institutions are preferred settings to explore prominent topics in the transnational approaches to the recent history of science. These include: the dichotomy between universalism and contextualism in the historical evolution of exact sciences; the historical transformation of the ideals of scientific internationalism; the tensions between these historically changing ideals and scientists’ national allegiances; the balance between scientific and diplomatic activities of such institutions; and the issue of how the complex ideological, socio-political roles these institutions play affected the actual evolution of science.

Inspired by these overreaching themes, the paper presents a conceptual framework for pursuing a comparative analysis of IAU and IUPAP. A bird’s-eye view of the parallel historical developments of these two unions shows that, in spite of their common origins in the highly politicized context of the post-WWI reconstruction of international cooperation, IAU and IUPAP followed diverging trajectories in many respects. It is argued that a deeper study of these differences might give important insights to properly understand the relevance of specific disciplines’ scientific needs in the way the ideals and practices of scientific internationalism were actualized through the 20th century.

India was still a British colony when the International Astronomical Union was born in 1919. India did not have a national science academy nor a national research council at the time. The Royal Society, London, which was the adhering body of Great Britain to IAU, handled matters of the colony too. India formally joined the IAU in 1948 as an independent nation through an initiative taken by the Government of India. In 1968, the National Institute of Sciences of India (NISI) became the adhering organisation to the IAU, as did the other affiliate Unions of ICSU. Soon after, its name was changed to Indian National Science Academy (INSA).

Till the nineteen-sixties, individual Indian membership in the IAU grew rather tardily but the situation changed with the rapid growth of astronomical activities in the country. In 1967, M.K. Vainu Bappu, the then Director of the Kodaikanal Observatory, was elected a Vice-President of the Union. In 1979, he was elected the President of IAU for the triennium 1979–1982, and during the same period, V. Radhakrishnan and Govind Swarup were elected Presidents respectively of the Commisions 34 and 40. In 1985, the General Assembly of the Union was held in New Delhi. It was dedicated to the memory of Vainu Bappu who had initiated the process of inviting the Union to hold its GA in India. A few years later the Sixth Asian-Pacific Regional IAU Meeting was held in Pune. A number of IAU symposia and colloquia have also been held in the country. During the last three decades, the engagement of the Indian astronomers with IAU has increased a great deal with a large number of them taking on important official roles in the IAU. Currently, India has close to 300 individual members.

Just as in the past, the development of the natural sciences and in particular of astronomy has changed the history of humanity. If we think about the role of our discipline into the future, it shows its enormous power in the field of education, owing to the possibility of awakening interest in science in very varied audiences. Within the framework of the enormous progress made in the technologies related to astronomy, many of them of daily use, the role of the astronomer in the era of Communications acquires fundamental importance.

In this presentation, we will try to make a journey through the different ways of presenting astronomical topics for different audiences over the last 100 years. In turn, we will show some specific achievements, associated with education programmes of the discipline. We discuss the impact produced by proposals that are both rigorous in terms of content, and also appeal to the development of the human being in an integral manner, within the framework of citizen science activities.

For this research, we have taken into account the uninterrupted development of the NASE programme, which has performed 112 courses in 24 countries throughout the world and in different languages. NASE has involved 4966 secondary teachers in the last eight years.

Nicolae Donitch gave a special role to Romania’s membership of the IAU, even though it had basically adhered to it in 1922, but only on the 12th of July 1928 was Romania’s membership in the IAU recognized. He was a passionate observer of eclipses, of the zodiacal light, and a good instrument builder. His tortuous destiny was somehow similar to the destiny of many Romanians from Eastern Moldova: he was born in Chişinău, the capital of Bessarabia at that time; he studied in Odessa; after the first revolution in February 1917 he left Russia and remained in Odessa until the arrival of the Bolsheviks in 1920, who would completely destroy his laboratory. He then moved to his private Astrophysics Observatory in Dubăsarii Vechi, which he had set up in 1908, and stayed until 1940, when Bessarabia was once again torn away from Romania. He relocated to Bucharest, but soon after, when communists came to power, he had to leave the country on a permanent basis. As he severed all the ties with people from the country that had fallen into the red zone of communism, we completely lost track of him. It was only recently that, after thorough research, we could discover his traces, and learn of his last years of life.

This paper discusses the main outcomes of the International School for Young Astronomers (ISYA), an IAU programme developed since 1967 under the auspices of Commission 46 Astronomy Education & Development, at present Commission C1. An assessment of the impact of the ISYA is given from various surveys and communications with the participants and organizers of the past ISYAs.

We describe the history of solar-eclipse supervision since the formation of the International Astronomical Union, as the supervising body morphed from a full commission to a subcommission to its current status as an Inter-Divisional Working Group of the Education, Outreach and Heritage Division and the Sun and Heliosphere Division.

This paper discusses my time as IAU General Secretary, 1967–70 and the General Assemblies in Prague in 1967 and in Brighton in 1970. I cover my work with Jean-Claude Pecker, whom I succeeded as General Secretary and with Donald Sadler, who was General Secretary 1958–64. The work of J. Kleczek for the International Schools for Young Astronomers is discussed.

IAU Commission 41 (History of Astronomy) was founded in 1948, and between 1991 and its termination in 2015 this Commission hosted seven different Working Groups (one of which was shared with Commission 40 (Radio Astronomy). In this paper we list the objectives of these seven Working Groups and track their progress. We conclude by evaluating the role that each C41 Working Group played in furthering research on the history of astronomy.

Beginning in year 2000 the IAU undertook a number of initiatives that changed the Union from being primarily an inward-focused organization whose emphasis was the world of professional astronomy, to being more outward looking in engaging with the public. These initiatives included proposing to the United Nations and then leading the International Year of Astronomy IYA 2009, and the formulation of a Strategic Plan that included creation of the Office of Astronomy for Development. Additional programs are being undertaken by the Union that continue to broaden IAU engagement with the public.

After the foundation of the International Astronomical Union (IAU), it took nearly 32 years until Germany became a national member of the IAU. This unfortunate delay was due to both international politics and discussions within Germany (e.g. about the future role of the Astronomische Gesellschaft). The first Statutes of the IAU of 1919 excluded Germany, Austria and other countries from membership for political reasons. When the IAU Statutes were revised in 1931, Germany’s membership was possible, but could not be realized because of financial problems. In the mean time, German astronomers (as individuals) were often able to attend General Assemblies of the IAU as invited participants and to work in IAU Commissions as members. After World War II, Germany became a member of the IAU in 1951, Austria in 1955. In 1962, East Germany was accepted as an additional member. The reunification of Germany in 1990 clarified this situation. Member of the IAU is now one unified Germany.

Continuous regional cooperation is efficient and constructive for long-term development of astronomy, as clearly shown by the great success of ESO in the European Region. The IAU does not formally define its Regions, however they are becoming clear through the Regional Meetings during recent decades. We present some statistics and considerations about five IAU Regions, based on the temporarily assumed geographical distribution of IAU National Members. For further growth of IAU and worldwide astronomy, the role of Asian Pacific, Lain American, and Mid-East & African Regions is essentially important. We can identify three groups; “Super”, “Advanced”, and “Developing” groups of IAU National Members based on the rate of IAU Individual Member per population in each of the National Members. This rate, identical to the number of astronomer per head of population, can be regarded as an indicator of the “strength” of astronomy in each of the NMs, while the number of Individual Members indicates the “size” of astronomical research. We find that the distribution of this rate shows clear differences from Region to Region. Based on this analysis, we propose planning within IAU National Members, each Region and the EC so as to grow from a “Developed” group to an “Advanced” group, as well as to increase the number of NMs. The IAU should encourage and support those efforts by National Members and Regions through the platform of Regional Meetings, the OAD and other possible strategic programmes.

This year 2018 has great historical and current significance for stellar spectral classification. Two hundred years ago in Reggio Emilia, Italy, was born Angelo Secchi, a pioneer of observing and classifying the spectra of stars. At the beginning of the IAU, almost a hundred years ago, one of its original Commissions was entitled the Spectral Classification of Stars, from which was generated Commission 45, Spectral Classification and Multi-band Colour Indices. And seventy-five years ago, was published the system-changing MKK, An Atlas of Stellar Spectra. Through this necessarily brief, historical view we shall recall how spectral classification, supported internationally by the IAU, continually updated its techniques, while remaining anchored to standards. This has ensured that the MK classification process stays very relevant to the initial characterizing of stars in the 21st century era of large spectral surveys.

The USA delegation to the July 1919 International Research Council meeting in Brussels included Joel Stebbins, then professor of astronomy and observatory director at the University of Illinois, as secretary of the executive committee appointed by the National Research Council. Stebbins, an avid photographer, documented the travels of their party as the American astronomers attended the meeting and later toured devastated towns, scarred countryside, and battlefields only recently abandoned. Published reports of the meeting afterward attest to the impression left on the American visitors, and the photographs by Stebbins give us a glimpse through their own eyes. Selected photographs, recently discovered in the University of Wisconsin Archives and never before publicly seen, will be presented along with some commentary on their significance for the International Astronomical Union, which took shape at that 1919 meeting.

“Urania” is a popular Polish astronomy magazine, one of the oldest in the world among present journals of this type. The first official issue was published in 1922, but the origins of “Urania” are even older, as in 1919 and 1920 there were published a few issues of a predecessor of “Urania” with the same title. So we can say that “Urania” and the IAU are of the same age. The role of “Urania” has been changing during these 100 years, but the magazine has been always a very important entity for the astronomical community in Poland, both professional and amateur. Thousands of pages contain an historical record of astronomy in Poland, as well as the progress of astronomy in the world, including IAU activities.

In this paper I discuss the general role of the IAU General Secretary, and reminisce on the XXIst IAU General Assembly in Buenos Aires, Argentina in 1991, where a fire disrupted proceedings on the final days.

Astronomy in Japan has long history and has its own “light”. The foresight of leaders in the early 20th century helped Japan to become a founding member of the International Astronomical Union. In this paper, a brief description will show the growth in its more recent history with particular emphasis on two important issues: large research facilities and women participation. On the ground or above, the large observational facilities are nowadays outside of the land of Japan, not only in terms of physical presence but also the community they serve. Domestic membership of the Astronomical Society of Japan at the same time is expanding, thanks to the increased opportunities for women. Continuing global cooperation with more diverse composition of members are the keys for sustaining the growth to carry the astronomy in Japan with IAU into the next century, and hopefully to another planet.

One hundred years ago, the International Astronomical Union was created, one of the very first Unions dedicated to the advancement of a discipline and the promotion of international collaboration and exchange. In 100 years, astronomy has made huge progress, and the IAU has greatly expanded in volume and purpose. In recent years, it has become more and more active in education, astronomy for development and dissemination of astronomy to a large public.

Even though Italy officially joined the IAU in 1921, Italian astronomers were involved in its birth as early as 1919, when Annibale Riccò, Director of the Astrophysical Observatory of Catania, proposed to the IAU Committee to hold its first General Assembly in Rome. This contribution will analyze the role played by Italian astronomers in the development of the IAU from its foundation to the Second World War. The recent project of reordering of the astronomical historical archives in Italy permits for the first time a more in-depth study of the relations between Italian astronomers and the international scientific community.