Teske, Johanna
Johanna Teske is a Staff Scientist at the Carnegie Earth and Planets Lab in Washington, DC. She is interested in understanding the diversity of exoplanet compositions (and how similar they are to the Earth) by studying their host star compositions and finding new small, rocky exoplanets. Johanna wants to bring inquiry design into a summer internship program for astronomy undergraduates, giving them experience with authentic research skills that they can apply throughout the summer and in their future astronomy endeavors.
jteske@carnegiescience.edu

Teaching Activity Summary
Name of Teaching Activity: The Accelerating Universe
Teaching Venue & Date: Carnegie REU, August 10, 2018
Learners: 10 undergraduate students.
Reflection on teaching and assessing the core science or engineering concept
Our content goal for the students was for them to understand that the expansion rate of the universe has changed over time and is accelerating. We hoped to elucidate this goal, and it’s direct implications, by having the students use different cosmological fits to astronomical data to derive the age of the universe. This concept is central to understanding the broad history of the universe, and thus how different objects we observe fit into that picture. There are multiple ways to constrain this history, with Type Ia SNe being particularly important to the practice of astronomy at Carnegie in the past and now.
The students in our cohort came from a range of backgrounds, so we thought it was probable that at least some of them held the common misconceptions that the universe is expanding outward from a single point, and/or that the expansion of space is different than objects moving away from each other through space. Frankly, the deeper understanding of exactly how we know from observations the expansion history of the universe was something we struggled with throughout the creation of the activity, and we have PhDs!
We assessed the students’ understanding during a mock poster session. The dimensions of the concept we were looking for students to demonstrate were Astronomers use cosmological redshift to determine the distance to astronomical objects The expansion rate of the universe has changed over time and is accelerating The age of the universe depends on its expansion history We decided after we taught the lesson that the first dimension probed directly by our activity, because we didn’t spend enough time emphasizing how redshift is the observed quantity and distance is the modelderived quantity. The second dimension turned out to be muddied by our own understanding of how the measurements are interpreted, so while all of the students grasped that the expansion rate has changed over time, when it was accelerating was actually falsely concluded from the activity. For the third dimension, we thought about half of the students understood this concept by what they said in their poster presentations, but about half did not. Those that did not mostly understood that there was a “best fit” cosmological model, but didn’t take the next step to suggest what that implied for their resulting age of the universe estimation.
If I taught this lesson again, I think I would try to modify it so that the first content dimension was more explicitly addressed in the lesson, and I would try to make clearer to students the boundaries of the investigation, e.g., that looking up what the “right” cosmological parameters are is not conducive to them developing an understanding of the influence of those parameters