Lessons from a Lesson on Stellar Evolution

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Categories: GSI Online LibraryTeaching Effectiveness Award Essays

by Kathryn Peek, Astronomy

Teaching Effectiveness Award Essay, 2005

Astronomy comprises many difficult concepts that are often obscured by unfamiliar terminology. In the middle of the semester, as motivation begins to wane, the 840-student Astronomy 10 covers stellar evolution, one of the most jargon-heavy components of the course. Students are faced with gleaning the story of a star’s lifetime from a barrage of vocabulary; “Type Ia supernova,” “Type II supernova,” “neutron star,” “pulsar,” “red dwarf,” “brown dwarf,” “white dwarf,” “black dwarf” are thrown at students in rapid succession. Realizing that discussing the finer points of stellar evolution was being complicated by students’ difficulty with such terms, I set out to create a lesson that would help them solidify the paths stars follow during their lifetimes.

The activity I developed for my discussion sections was very straightforward: in groups of five or six, students worked at the boards to create a flow chart of sorts to map each phase of stellar evolution. Mass is the quantity that determines the path a star follows during its lifetime, so I started by writing on the board at the front of the room the three major mass ranges and a randomly-ordered list of all the stellar phases they were to weave into the flow charts. The students diagrammed the life cycles of the three types of stars, consulting with one another and occasionally asking me questions as I circled the room. When they finished, I brought the class back together and talked through the stellar sequences, answering any remaining questions. The whole activity took about half an hour. By the end of their independent time, not only did most groups have the correct flow chart, but more importantly, they had used and discussed all the terms, making everyone more familiar with their definitions.

The virtues of my lesson were that it was interactive and simple, and that it had a worthwhile outcome. Having students work at the board encouraged everyone to participate because they were up out of their seats. The small-group aspect was important because with thirty-five students, section-wide discussions are difficult. And since it required only board work, the exercise was easy to implement. (It also proved far more effective than flashier lessons that had required about five times the preparation.) My indication that the lesson was worthwhile came from my students. Both my sections seemed to enjoy it; conversation was livelier than usual as they worked together to sort out stellar evolution. When, at the end of section, I asked the class as a whole whether the lesson had been instructive, my question was met with emphatic nods and resounding statements of “yes!” Also, several students approached me independently after class to stress that the exercise had been useful for them, and many commented on the semester-end evaluation forms that activities had been the most helpful aspect of section.

The stellar evolution exercise followed from a tenet of my teaching philosophy: occasionally putting larger concepts aside to nail down the basics is important, and doing so can illuminate more complex ideas. By pinpointing that pulsars are a subset of neutron stars, which form from Type II supernovae, students give pulsars a context, and putting ideas in context helps students to remember them. The day that I did this exercise in my sections was one of my best days that semester; I did something simple that helped my students immensely, and in return, my students gave me the positive feedback I needed to remind me why I decided to teach in the first place. And I learned something, too: in astronomy, uncomplicated lessons can be the key to teaching complicated ideas effectively.