Astronomy Education Research Observations from the iSTAR international Study of Astronomical Reasoning Database

Historically, an important part of the scientific research cycle is to situate any research project within the landscape of the existing scientific literature. In the field of discipline-based astronomy education research, grappling with the existing literature base has proven difficult because of the difficulty in obtaining research reports from around the world, particularly early ones. In order to better survey and efficiently utilize the wide and fractured range and domain of astronomy education research methods and results, the iSTAR international Study of Astronomical Reasoning database project was initiated. The project aims to host a living, online repository of dissertations, theses, journal articles, and grey literature resources to serve the world's discipline-based astronomy education research community. The first domain of research artifacts ingested into the iSTAR database were doctoral dissertations. To the authors' great surprise, nearly 300 astronomy education research dissertations were found from the last 100-years. Few, if any, of the literature reviews from recent astronomy education dissertations surveyed even come close to summarizing this many dissertations, most of which have not been published in traditional journals, as re-publishing one's dissertation research as a journal article was not a widespread custom in the education research community until recently. A survey of the iSTAR database dissertations reveals that the vast majority of work has been largely quantitative in nature until the last decade. We also observe that modern-era astronomy education research writings reaches as far back as 1923 and that the majority of dissertations come from the same eight institutions. Moreover, most of the astronomy education research work has been done covering learners' grasp of broad knowledge of astronomy rather than delving into specific learning targets, which has been more in vogue during the last two decades. The surprisingly wide breadth of largely unknown research revealed in the iSTAR database motivates us to begin to synthesize the research and look for broader themes using widely accepted meta analysis techniques.