Using astronomical photographs to investigate misconceptions about galaxies and spectra: Question development for clicker use

Many topics in introductory astronomy at the college or high-school level rely implicitly on using astronomical photographs and visual data in class. However, students bring many preconceptions to their understanding of these materials that ultimately lead to misconceptions, and research about students’ interpretation of astronomical images has been scarcely conducted. In this study we probed college students’ understanding of astronomical photographs and visual data about galaxies and spectra, and developed a set of concept questions based on their common misconceptions. The study was conducted mainly in three successive surveys: (i) open-ended questions looking for students’ ideas and common misconceptions, (ii) combined multiple-choice and open-ended questions seeking to explore student reasoning and to improve concept questions for clickers, and (iii) a finalized version of the concept questions used to investigate the strength of each misconception among the students in introductory astronomy courses. This study reports on the procedures and the development of the concept questions with the investigated common misconceptions about galaxies and spectra. We also provide the set of developed questions for teachers and instructors seeking to implement in their classes for the purpose of formative assessment with the use of classroom response systems. These questions would help them recognize the gap between their teaching and students’ understanding, and ultimately improve teaching of the concepts.

Figure 1

The Milky Way observed at radio, infrared, and optical. Following open-ended questions were asked: These images are each of the same part of the Milky Way made from observations at radio, infrared and optical wavelengths. Why do you think the colors in the radio image look much different from the ones in the infrared or optical images?; Why do you think there is a bright horizontal band in the infrared image where the optical image mostly looks dark?; and, Why do you think the structures in the three images are different?

Figure 2

The Andromeda Galaxy. Following open-ended questions were asked: This is the photograph of the Andromeda galaxy. What do you think the thousands of tiny dots (such as A) are in this photo?; They belong to ___ a. Our Galaxy, b. The Andromeda galaxy, c. The empty space between our Galaxy and the Andromeda galaxy, d. None of the above; and, Why did you choose your answer in the above question?

Figure 3

Spiral Galaxy. Following open-ended questions were asked: This is a galaxy imaged by the Hubble Space Telescope. What is the yellowish area A in the photo? What causes it to have this appearance?; What are the dark features B? What causes them to have this appearance?; What are the reddish blotches C? What causes them to have this appearance?; What are the pale blue areas D? What causes them to have this appearance?; and, In the galaxy image, why do you think this object has the structure it does?

Figure 4

Elliptical galaxy (type A) and Spiral galaxy (type B). Following open-ended questions were asked: The photographs show two different types of galaxy. Why do you think their colors look different?; and, Why do you think they have different shapes?

Figure 5

Spectra: Red-shift. Following open-ended question was asked: (a) is the spectrum that was obtained looking at a nearby galaxy. (b) is the spectrum that was obtained from a distant galaxy. What explains the difference between spectrum (a) and spectrum (b)?

Figure 6

Spectra: Distance of galaxies. Following open-ended question was asked: These are spectra that were obtained from four different galaxies. Do you think with these spectra images you can arrange them by distances from nearest to furthest from us? If so, please do so and explain why you arranged them in such a way. If not, please explain why you can not do with these images.

Figure 7

Spectra: Stellar temperature. Following open-ended question was asked: These are spectra that were obtained from three different stars in our galaxy. Do you think with these spectra images you can arrange them by temperature from hottest to coolest? If so, please do so and explain the reason why you arranged them in such a way. If not, please explain why you can not do with these images.

Figure 8

Students’ performance on the Survey 3 at two introductory astronomy courses.