This thesis adds to the empirical research foundation of informal science education through an investigation of a museum-based astronomy internship for high school students, in the domains of attitudes toward science, knowledge of science, and participatory science learning. Results are presented as three studies, all using a qualitative methodology and including the methods of semi-structured interview, reflective journal, direct observation, audio recording, and artifact collection.

In the first study, four aspects of attitudes toward science were investigated. Results revealed that interns held mixed views of themselves as scientists, held positive attitudes toward science for four primary reasons, and provided twelve reasons for their pursuit of science activities outside of school. The internship also solidified interns' (largely science-related) careers aspirations.

In the second study, four aspects of scientific knowledge were investigated. After participation, the majority of interns believed teaching was part of the scientific enterprise. Interns also used at least six modes of scientific thought, only one of which was taught explicitly to them. The amount and depth of science content learned during the internship depended on interns' prior knowledge, and was learned during three specific aspects of the internship. Finally, interns used numerous science concepts during the internship, the most frequent of which were closely related to the internship activities.

In the third study, six aspects of participatory science learning were investigated. Results across the six domains indicated that interns found teaching to be the most salient aspect, viewing it as an authentic practice and a path to science learning, as well as providing a sense of ownership in their practices. Also, interns created a unique community within the internship, combining aspects of the pre-established museum educators' community of practice and an internship-centered activity group.

Looking across the three studies, both teaching and social interactions were found to be underlying factors in many of the results and represent two important concepts to understand this type of internship experience. There is also evidence for the learning of both contextualized and transferable science knowledge in the internship, suggesting further research in this domain.