Astronomy

Non-technical description: Both young (4-6 MYr) and old (>1 Gyr) stars orbit around Sag A*, the supermassive black hole at the center of our galaxy. How the young stars came to be there, in an area inhospitable to star formation, has been called the "Paradox of Youth". This work detects and spectroscopically classifies stars in an area slightly further away from Sag A* than previous studies with the goal of examining the edges of the young stellar cluster. We detect more than 300 stars in the area of study and find fewer young stars than expected from a standard power-law, which indicates an edge to the stellar cluster. Theoretically, this implies that the young stellar cluster formed when an immense gas cloud was drawn into the orbit of Sag A*. Stars then began forming out of the densely pressed-together gas.

Non-technical description: Among the stars detected in Støstad et al. (2015), some stars were found to have surprisingly low metallicity values (percentage of elements heavier than hydrogen or helium). Further research on this observation found a large range of metallicity values in the stellar cluster, and strengthened the hypothesis that the stars formed close to the Galactic center. As previous studies had found largely similar metallicity values close to that of the Sun, these results indicate that metallicity analyses will be more important for our understanding of the Galactic center than previously thought.

Abstract: Item Response Theory (IRT) is an advanced statistical method that measures the usefulness of questions as it varies with student ability. We present a new data set of 518 questions from University of Toronto’s AST101 and AST201, each question having been answered by over 1000 students. We create an online testing module built with IRT and computer adaptive testing (CAT) methods, which vastly increases both test accuracy and test efficiency from normal testing methods. Compared to past 50-question AST101 tests the online CAT module estimates ability at equivalent or better accuracy, with an average of only 13 questions per test. The test is used to measure the introductory astronomy ability of different groups of University of Toronto’s Astronomy Department. In the future a similar test could be used both to measure student gain over a semester, and for students to estimate their ability before examinations. As a second part of the project we also present tentative analytic results on the factors that need to be assessed when creating multiple choice questions, based on both quantitative and qualitative methods. These analytic results will be taken into account when creating future AST101/AST201 examination questions.