Astronomers like to present their discipline as the oldest science as well as the most international one. Who cares about earthly borders when contemplating the great beyond? Astronomers have claimed that their science has never been affected by worldly politics, even while recognizing the enormous impact of, say, the Cold War on astronomy. These claims have rightly been critically assessed by historians. Still, we should take them seriously, because the imagined past of astronomy is a core part of its disciplinary identity.
I will investigate astronomy’s internationalist self-image in the context of the history of the International Astronomical Union, founded in 1919 to promote international cooperation. Ever since, the IAU has struggled to find ways to fulfil this task while staying out of politics. In practice, most international collaboration in astronomy was shaped by mission-oriented organizations that aimed to build joint instruments, for example ESO and space agencies such as NASA.
After the end of the Cold War, the way the IAU represented the international astronomical community changed. At the same time, several developments forced the organization to engage more actively with the outside world, most notably the public outcry over the ‘demotion’ of Pluto to the status of dwarf planet. The IAU started to focus on outreach and popularization, under the banner of ‘Astronomy for Development’. This was a new and more active take on scientific internationalism.
