This qualitative study explores the pedagogical and curricular thinking of five
professional astronomers, faculty at a university, about teaching the Hertzsprung-Russell diagram in introductory astronomy courses for non-science majors. Data sources for this study included two semi-structured interviews per participant, in which they were asked about teaching the Hertzsprung-Russell diagram, as well as about the introductory course in general. In addition, participants were asked to complete four cognitive tasks; the creation of a lesson plan, a concept map on how they would like their students to think about the Hertzsprung-Russell diagram at the end of the course, a Pathfinder network rating task, and responding to stereotypical student statements regarding the Hertzsprung- Russell diagram.
The data was analyzed using a case study approach, followed by a discussion of themes that emerged from the data. Results indicate that participants had primarily affect and process goals for the course, rather than content goals. In addition, they wanted students to view the HR diagram as a part of a flow chart, where input physics (both observed and inferred properties of stars) leads to the construction of the HR diagram, which in turn is used to make inferences about stellar evolution. Participants identified several student difficulties with the HR diagram, among which interpreting a graph was the most pertinent. In several stereotypical student statements, participants responded using the exact same analogies to explain the concepts to the students. This may be indicative of some underlying pedagogical content knowledge.