The demands on the primary school teacher in delivering the National Curriculum in England and Wales at Key Stage 2 (KS 2) for children aged 7‐11 years are considerable. Public debate concerning teacher subject knowledge and understanding, particularly in science, has raised the issue of the need for increased specialism in the primary school. A core element of this debate has focused on how to develop teacher subject knowledge for the effective delivery of the Programme of Study (POS) at KS 2 for practising teachers. This has resulted in the increased provision of in‐service courses in higher education and has also impacted significantly on course content in initial teacher training. This paper relates to the ‘The Earth and Beyond’ POS exploring factors which contribute to developing teachers’ understanding of basic astronomical events. Results indicate that providing teachers with the necessary skills and confidence to teach this aspect of science effectively is much more complex than simply explicating science content knowledge. The findings suggest that what is needed is the explicit recognition of key features in supporting learning. These are identified and the implications for teacher education are discussed.