This paper presents the first iteration of development and classroom testing of Stars and Elements, a web-based learning resource for Norwegian upper secondary physics students focused on how heavy elements are produced in stars and neutron star mergers. Combining the model of educational reconstruction (MER) with the pedagogical link-making framework and design-based research (DBR), we identified core ideas to be communicated, reviewed the physics curriculum and research on student understanding and motivation, and formulated design hypotheses that guided development of a 90-min learning resource with animations, videos, interactive tasks, peer discussion, and teacher consolidation. Six classes ( = 120) participated; data comprised students’ written responses to three open tasks, brief evaluations, and classroom observations. Most students could describe central concepts and processes concerning red giant stars and neutron star mergers as sites for heavy element production, notably the slow and rapid neutron capture processes, and many benefited from animations and varied task formats. Some displayed uncertain grasp of concepts such as fusion and beta decay. Nature of science (NoS) aspects concerning how physics knowledge is developed were found to be insufficiently represented. From these findings, we propose design principles for research-based learning resources on similar topics, including emphasizing explicit link-making across scales and prior knowledge, scaffolding for challenging nuclear concepts, multimodal visualizations, and explicit NoS focus. We argue that combining MER, link-making, and DBR is a promising approach for developing learning resources that reflect the frontiers of science while having a solid grounding in the classroom.