In this paper, we report about the development and validation of a learning progression about the Celestial Motion big idea. Existing curricula, research studies on alternative conceptions about these phenomena, and students' answers to an open questionnaire were the starting point to develop initial learning progressions about change of seasons, solar and lunar eclipses, and Moon phases; then, a two-tier multiple choice questionnaire was designed to validate and improve them. The questionnaire was submitted to about 300 secondary students of different school levels (14 to 18 years old). Item response analysis and curve integral method were used to revise the hypothesized learning progressions. Findings support that spatial reasoning is a key cognitive factor for building an explanatory framework for the Celestial Motion big idea, but also suggest that causal reasoning based on physics mechanisms underlying the phenomena, as light flux laws or energy transfers, may significantly impact a students' understanding. As an implication of the study, we propose that the teaching of the three discussed astronomy phenomena should follow a single teaching-learning path along the following sequence: (i) emphasize from the beginning the geometrical aspects of the Sun-Moon-Earth system motion; (ii) clarify consequences of the motion of the Sun-Moon-Earth system, as the changing solar radiation flow on the surface of Earth during the revolution around the Sun; (iii) help students moving between different reference systems (Earth and space observer's perspective) to understand how Earth's rotation and revolution can change the appearance of the Sun and Moon. Instructional and methodological implications are also briefly discussed.

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[This paper is part of the Focused Collection on Astronomy Education Research.] In this paper we discuss the design and development of a learning progression (LP) to describe and interpret students' understanding about stellar structure and evolution (SSE). The LP is built upon three content dimensions: hydrostatic equilibrium; composition and aggregation state; functioning and evolution. The data to build up the levels of the hypothetical LP (LP1) came from a 45-minute, seven-question interview, with 33 high school students previously taught about the topic. The questions were adapted from an existing multiple-choice instrument. Data were analyzed using Minstrell's "facets" approach. To assess the validity of LP1, we designed a twelve-hour teaching module featuring paper-and-pencil tasks and practical activities to estimate the stellar structure and evolution parameters. Twenty high school students were interviewed before and after the activities using the same interview protocol. Results informed a revision of LP1 (LP2) and, in parallel, of the module. The revised module included supplementary activities corresponding to changes made to LP1. We then assessed LP2 with 30 high school students through the same interview, submitted before and after the teaching intervention. A final version of the LP (LP3) was then developed drawing on students' emerging reasoning strategies. This paper contributes to research in science education by providing an example of the iterative development of the instruction required to support the student thinking that LPs' levels describe. Concerning astronomy education research, our findings can inform suitable instructional activities more responsive to students' reasoning strategies about stellar structure and evolution.

This paper is part of the Focused Collection on Astronomy Education Research.] Several decades of research have contributed to our understanding of students' reasoning about astronomical phenomena. Some authors have pointed out the difficulty in reading and interpreting images used in school textbooks as factors that may justify the persistence of misconceptions. However, only a few studies have investigated to what extent usual textbook images influence students' understanding of such phenomena. This study examines this issue, exploring 13-14 year old students' explanations, drawings, and conceptions about three familiar phenomena: change of seasons, Moon phases, and solar or lunar eclipses. The research questions that guided the study were (RQ1) how are students' explanations and visual representations about familiar astronomical phenomena affected by different image-support conditions? (RQ2) How are students' conceptions about familiar astronomical phenomena affected by different image-support conditions? (RQ3) Which features of the used images most affected the students' visual representations and explanations of familiar astronomical phenomena? To answer our research questions, we designed three instructional contexts under increasing support conditions: textbook images and text, teaching booklets with specially designed images and text, only text. To analyze students' drawings, we used exploratory factor analysis to deconstruct drawings into their most salient elements. To analyze students' explanations, we adopted a constant comparison method identifying different levels of increasing knowledge. To investigate students' conceptions, we used a mixed multiple-choice and true false baseline questionnaire. For RQ1, results show that the specially designed images condition was effective in helping students producing informed drawings in comparison to text-only condition for all phenomena, and more effective than textbook images condition when one considers seasonal change drawings. Concerning RQ2, the specially designed images condition was the most effective for all phenomena. Concerning RQ3, prevalent elements of astronomy images that affected students' explanations and visual representations were Earth's elliptical orbit; the position of the Sun with respect to the Moon orbit; and Sun, Moon, and Earth alignment. Our findings confirm concerns about textbook astronomy images, whose features may interfere with the identification of the relevant factors underlying the phenomena. Moreover, findings of this study suggest that affordances of the specially designed images may play an essential role in scaffolding meaningful understanding of the targeted phenomena. Implications for teaching through and learning from visual representations in astronomy education are briefly discussed.