Connecting Points in Time: From the Evolution of Clouds in Substellar Atmospheres to Students’ Perceptions of Earth’s Place in the Universe

Abstract

Equally as important as growing the body of human knowledge through scientific discoveries and analysis is relaying this information to the general public in a digestible manner to establish a scientifically literate society. This dissertation approaches the multifaceted issue by combining an in-depth study of brown dwarf binary atmospheres with an astronomy education component. Thus, the goal of this work is twofold: to improve our current understanding of clouds in brown dwarf atmospheres and to identify preconceptions non-science undergraduate students posses about Earth's place in time and space in the Universe. The first portion of the dissertation seeks to constrain atmospheric and cloud properties in a sample of well-known brown dwarf binaries. I answer this question using spatially-resolved optical and near-infrared photometry from the Hubble Space Telescope (HST) and the W. M. Keck Telescopes to explore cloud properties in detail across a broad range of effective temperatures and surface gravities. New grids of synthetic spectra were created using the PHOENIX atmosphere model code, extending clouds to deeper pressures and smaller mean grain sizes. I report bulk atmospheric properties with trends in cloud location and mean grain size for mid-L through mid-T type brown dwarfs (Chapter 2). The results of this study led to a detailed analysis in Chapter 3 of an individual triple system, HD 130948, containing a solar analogue star and two brown dwarfs of similar mass, luminosity, and spectral type. Moderate-resolution spectroscopy from the OSIRIS instrument on Keck was fit to synthetic spectra to determine the best-fitting atmosphere parameters of HD 130948B and HD 130948C for solar and stellar metallicity. I measure the C/O ratio of each binary and confirm it is consistent with the host star. In the second component (Chapter 4), I investigate students' conceptions of time in astronomy as it relates to Earth's formation and location in the Universe. A set of open-ended questions were developed and issued to a sample of students in an astronomy course. Thematic analysis of the responses suggested students struggle with fundamental topics in astronomy related to the origin and formation of the Universe, planet formation, the age of the Universe and Earth, and the composition and structure of the Universe. Incorporating explicit discussion and instruction regarding time in astronomy can be a useful tool toward improving non-science students' grasp of difficult, abstract concepts in introductory astronomy courses.