The founding and development of two commissions of the IAU that played a unique role in IAU history are traced. Commission 38 for the Exchange of astronomers was founded in 1946 with Frederick Stratton as first president, and it expended funds (initially granted by UNESCO) for astronomers to travel on exchange visits. Commission 46 for the Teaching of astronomy was founded in 1964 with Evry Schatzmann as first president. This was a time of rapidly growing interest in the IAU for teaching astronomy and in due course for promoting astronomy in developing countries. For a while, both commissions operated under the wing of the Executive Committee. Their role was unique as they were the only IAU commissions to have their own budget, as well as aspiring to bring about social change in the astronomical community. By 2000 both commissions merged into C46 (Astronomy education and development) and by that time various programmes such as the International School for Young Astronomers (ISYA), the working group World-wide Development of Astronomy (WWDA) and the working group Teaching Astronomy for Development (TAD), which grew out of the Visiting Lecturers’ Program (VLP), were all run by C46. When the IAU established the Office of Astronomy for Development in 2011, many of these functions were removed from the commission and in any case C46 ceased to exist in 2015 when all the old commissions were disestablished. In 2015 the Office for Young Astronomers took over the running of the ISYA. The history of C38 and C46 represents a time of active change in the way the IAU was engaging with people. It was more than just a union for scientific research, but in the world of scientific unions, it was remarkable for taking an active hands-on role in implementing social change. In the history of these two commissions, the Swiss astronomer Edith Müller played a leading dynamic role. She served as president of C46 (1967-73), of C38 (1985-88) as well as IAU General Secretary (1976-79).

OAD, the Office of Astronomy for Development, one of the most significant innovations within the IAU, was created at the XXVII General Assembly in Rio de Janeiro in 2009 and opened in 2011. The new office brought together and strengthened several activities of the IAU aimed at helping astronomers in developing or isolated countries to keep in touch with their colleagues elsewhere and up-to-date with the developments in our science. Those activities were mediated through the old commission structure by Commission 38 (Exchange of Astronomers) and Commission 46 (Astronomy Education and Development) which oversaw the International Schools of Young Astronomers (ISYA), the Visiting Lecturer Programme (VLP) and Teaching for Astronomy Development (TAD). In addition, Jorge Sahade, during his term as IAU President (1985–1988), formed the Working Group for the Promotion and Development of Astronomy, as a sub-committee of the Executive Committee, and asked the present writer, then a Vice-President, to act as chair. That Working Group (later renamed the Working Group for the Worldwide Development of Astronomy, WGWWDA) operated within the context of the already existing services of the IAU and in cooperation with the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS). In this paper, the writer gives an account of the activities of the WGWWDA both during and between General Assemblies, until the year 2000, shortly after which he relinquished responsibility for them.

During the 100 years of the International Astronomical Union, the worldwide astronomical publications have grown exponentially, converted almost entirely to English, and changed format from observatory publications to journals to online publications. Observatory publications, conference proceedings, and individual theses have nearly disappeared in usefulness for research.

The history of the International Astronomical Union (IAU) meetings goes back to 1922 when the first IAU General Assembly (GA) was held in Rome, Italy, following the IAU creation in 1919. However, until 1953, no individual symposia were organized and the GAs were the only official gatherings for astronomers. All together, eight IAU GAs were held during 1922–1952. The IAU Symposium 1 was held in 1953 in Groningen, Netherlands. Starting with 1955, several IAU symposia were regularly held in different places, and since 1959, the IAU also began to organize colloquia to discuss relatively smaller topics. Twenty IAU colloquia numbered as I–XX were held in the period 1959–1971, and another series of IAU colloquia was organized in 1968–2005, numbered as Nos. 1–200. At present IAU symposia are the only official scientific meetings, nine of them being organized every year. IAU S349 “Under One Sky: the IAU Centenary Symposium”, held in Vienna during the IAU GA XXX, was the last one by number in 2018. Thus, the IAU has a 65-year history of symposia and all together 348 such meetings have been held, on average 5–6 annually. At present most of the IAU symposia during the years of GA are being organized in the framework of the GA, there being typically six symposia during each GA. All together, 31 IAU GA have been organized during the years 1922–2018, including 30 regular ones and one Extraordinary GA (1973 in Warsaw, Poland), typically once every three years. Since 1974, the IAU has also organized regional meetings in Europe, Asia and Pacific (APRIM), Latin America (LARIM), and the Middle East and Africa (MEARIM). The European ones were discontinued in 1990 after the creation of the European Astronomical Society (EAS) and the organization of the yearly JENAM/EWASS. The 348 IAU symposia have been organized in 43 countries. We give the statistics of all IAU symposia by year of organization, by various topics of astronomy and astrophysics, and by host countries and cities.

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.

This work aims to present the partial results of a project to collect and analyze all the issues of the Newsletters of Commission C1 (Astronomy Education and Development), formerly named Commission 46. The sources and the (hard) work to obtain printed editions, digitalize and make them available on the Internet are shown. Over 40 years, 86 issues from 1977 until 2017 were published. The Newsletters list the structure of the Commission featuring the names of presidents, vice-presidents, organizing committee, editors, printing and distribution responsible with editorial and presidential letters in the cover. A preliminary analysis of contents of the published material is done. The results present the main subjects of stories that were related to papers, teaching materials, book reviews, courses and meetings. Many solar eclipses and other phenomena were reported. Reports of important projects of the commission were published, such as: International Schools for Young Astronomers (ISYAs), the travelling telescope among others WG projects. Stories of travels and triennial reports from many countries were continuously published presenting many actions and activities for all school levels, non-school activities such as planetariums and many other astronomy subjects. Reports of the education sessions and business meetings held during the IAU GAs and projects in developing countries complemented these publications. Occasionally, papers dealing with great questions and subjects can be found. There are many published contributions that show the participation of many members from many countries and the efforts to improve the astronomy education throughout the world. The surveyed material can be very useful for the next generations of astronomy education researchers, practitioners and teachers, not only as a repository of historical documents, but also as an inspiration for future projects.

“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 1539 the Italian Giovanni Paoli, better known as Juan Pablos, began operating in Mexico City the first printing press that existed in the New World. The first books he printed were religious texts, vocabularies of some indigenous languages of Mexico, and compilations of ordinances and laws. In 1556 followed the Sumario compendioso de las cuentas, a text of arithmetic and algebra that was the first American mathematics book. A year later, he printed the Physica Speculatio by friar Alonso de la Veracruz, a text of Natural Philosophy that dealt with Aristotelian works such as Physics, On the Heavens, and Meteorology. As part of this book, was included the text of geocentric astronomy written during the thirteenth century by the Italian mathematician Giovanni Campano de Novara, entitled Tractatus de Sphaera, where the author discussed, from a geometric perspective, the cosmic structure and the stellar distribution. No doubt this is the first astronomical treatise that was published in the entire American continent, which is why it is emphasized here.

Publications of the International Astronomical Union (IAU), such as Proceedings of IAU Symposia and Colloquia, contain biographical notes and papers as well as obituaries. Of great value are also the death announcements in the IAU Information Bulletins that contain the only biographical data known for about 200 astronomers. The kind of data given in these announcements varied over time. References to these data can be found in the Biographical Index of Astronomy. Recently the printed announcements were replaced by entries in the on-line IAU membership database.

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.

The 5-decade old ISYA program is evaluated in the context of the experience gathered in the field: 41 schools organized in 27 countries with a total of more than 1400 students to date. In the new era of fast internet connectivity, social media, virtual networks, big data and machine learning, the value of face-to-face graduate schools for regions with limited up-to-date astrophysics research is presented, together with the plan to develop the ISYA program into the next decade.

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.

The Night-Sky Observation Program (POC, acronym in Portuguese for Programa de Observação do Céu) is the most traditional education activity run by the Museum of Astronomy and Related Sciences (MAST), located in Rio de Janeiro, Brazil. The activity starts with a brief talk about the astronomical objects available for visibility and is followed by the sky observation with MAST’s telescopes, one of them being over a century old. A study conducted in 2015 pointed out that its participants perceive the historical value of the old refractor and declare that the activity brings them feelings of wonderment. These perceptions and declarations have motivated us to conduct a new study to identify and exchange experiences with institutions worldwide that also use historically valuable telescopes in their night-sky observation activities with the public. With the goal of gathering information from these institutions and making it into a guide, an online survey with open and close-ended questions was launched in late 2017. Nearly eighty institutions from all continents answered our questionnaire. The data collected are vast and rich and not only tell about the passion of those mediating such activities, but also the history of astronomy itself.

Inspiring Stars (IS) is an itinerant international exhibition promoted by the International Astronomical Union (IAU) to disseminate world initiatives addressing inclusion in astronomy at the professional level. It encompasses (but is not limited to) outreach, teaching and professional aspects of astronomy, with the ultimate goal of evolving from a levelling the playing field to egalitarian participation by all. Here we present the work-in-progress, a framework of bridging activities and inclusion in the social context, which may provide Inspiring Stars with the potential to motivate the next generation and to document comparable data on inclusion in astronomy.

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.

The research about women in astronomy began in 1988 following a request received from Wilfried Schröder, now deceased but, at that time, in charge of the Interdivision Commisssion on History, which was included in the International Association of Geomagnetism and Aeronomy (IAGA) attached to the IUGG International Union of Geodesy and Geophysics. The results obtained concerning “Astronomy, Geophysics and Women”, presented at the symposium “The history of geomagnetism and aeronomy”, were published (Débarbat 1989) in Advances in Geosciences in the form of a short paper. The IAU began to publish, in 1992, membership statistics in its Information Bulletin IB 68, including percentages of women and men, and several papers were published on the subject up to the last one Statistics on Women in IAU Membership (Débarbat 1989). Recent results are given including examples from the past.

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.

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.

Of all the sciences, astronomy is by far the most border-less in its activities, and the most advanced in its concepts of collaborating across borders. In their dealings and in their needs, today’s teams are mature enough to ignore gender differences and ethnic differences, and across the past 50+ years of IAU membership which I personally can chalk up, the IAU personnel, Commissions, and other bodies have come to reflect more nearly the same – albeit small – gender ratios as found in its member institutions. In the IAU there has always been space for the individual, and if one recalls the early contributions to the IAU by major players like Edith M¨uller, Giusa Cayrel, Anne Underhill and Charlotte Moore, I think it can be said that astronomy was, and knew it was, better off by giving such people the latitude that they deserved as scientists, rather than because they were women. When a meeting in Baltimore in 1992 was called to discuss “Women in Astronomy”, the pressure came from the younger generations, who feared that the low percentages of tenured women in astronomy would be allowed to continue unnoticed, so they created the Baltimore Charter to draw attention to what certainly appeared to some as discrimination. Even though there could be no quick fixes to the situation, and the winds of change have been more like zephyrs than the cleansing gales that some hoped for, the percentage of women now rising through the ranks is definitely on the increase, and is witnessing growing ethnic diversity. Those are a matter of pride for the IAU, and must be highlighted in this its Centenary Year.

The astronomical community accepts the division of the celestial sphere into 88 constellations, according to what was established by the IAU. In the first Assembly of 1922 the use of Latin names for constellations and their abbreviations was resolved. The pending issue of the limits of the constellations was discussed in the next meeting and Eugène Delporte had the responsibility for the complete theoretical demarcation. For his work, Delporte took into account what was done half a century earlier in the famous work Uranometría Argentina, published in 1877 and 1879, under the supervition of Benjamin Gould. In ths presentation we discusse the situation at the moment when the constellation boundaries were proposed using arcs of RA circles and parallels of declination, choosing them in such a way that they did not deviate too much from those used in the most important celestial atlas of the time, and minimizing the changes of which constellations stars would belong to.