Digital video fulldome has long been heralded as a revolutionary educational technology; yet the discipline-based astronomy education research literature showing planetarium effectiveness has been sparse. In order to help understand to what extent immersion impacts learning and the effect of the "narrative journey" model of presentation, we conducted a pre- and post-test effectiveness study of lectures on moon systems in the Solar System presented to 781 college undergraduates under immersive and non-immersive treatment conditions. Although all students showed some learning gains immediately after instruction, those who saw presentations in an immersive fulldome planetarium showed the greatest retention, compared to control classes that witnessed the same lecture and visuals on a flat screen in their regular classroom, and students that saw no interactive visuals. Because the same instructors, presentation visuals, and instructional outline were used for both the classroom and dome instruction using the virtual environment, the results suggest that the large display and wide field-of-view, two elements unique to the dome, resulted in greater attention, and were primarily responsible for the greater gains.