Ground-based astronomy is experiencing a new era of discoveries, largely thanks to the spread of new large-scale and cutting-edge observatories across remote areas worldwide. As a new generation of space-oriented research infrastructures and systems take the centerstage, questions over the social and environmental sustainability of these remain mostly unanswered. Displaying interdisciplinary approaches rooted in urban political ecology my research investigates conflicting assemblages between the unescapable weight of material flows and the influx of compelling imaginaries of just sustainabilities and scientific progress in large observatories in Chile, South Africa and Australia. Our research contributes to assess astronomy’s sustainability narratives and practices, providing feedback and social accountability to space science. In a wider perspective, our work aims to shape fair and non-colonial practices for humanity in space.