Thesis (PHD)--University of Montana, 2009. / Contents viewed on December 18, 2009. Title from author supplied metadata. Includes bibliographical references.

Thesis (M.S. in environmental science)--Washington State University, August 2009. / Title from PDF title page (viewed on Sept. 22, 2009). "School of Earth and Environmental Sciences." Includes bibliographical references (p. 92-97).

Not available / text

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 118-138).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Our solar system is just one of billions in the Milky Way, situated about half way from the Galaxy's core to its edge, and nestled safely between a pair of spiral arms. Out of those billions of planets, ours is the only one that we know to support life. This begs two questions. First, is our location in the Galaxy especially suitable for life? Second, if we want to find other life out there, where should we focus our search? In this dissertation, I contribute answers to both questions by seeking to better understand the boundaries of the Milky Way's galactic habitable zone (GHZ), the place in the galaxy where habitable worlds are most likely to be found. We start in Chapter 2 by introducing a novel method for finding the average height of surface features on exoplanets, a characteristic that influences a planet's habitability but was heretofore unknowable. We use elevation data for the rocky bodies in our Solar System to simulate their transits in front of stars of different sizes. We provide a relationship between the scatter at the bottom of the resulting light curves and the so-called "bumpiness" of the transiting planet. In Chapter 3, we zoom out from planets to get a better understanding of the dynamical and chemical evolution of the Milky Way, which are both crucial for constraining the Galaxy's GHZ. We use the Extreme Deconvolution Gaussian Mixture Model to identify overdensities of stars in both velocity and action space, called moving groups and orbit groups, respectively. Velocities and actions are calculated using data from the early third data release of the Gaia mission. When we analyze the chemical abundance distributions of these moving and orbit groups with GALAH DR3 data, we find that using velocities alone to define moving groups, or even using velocities and actions together, yields an incomplete view of the underlying density distributions and their origins. Our chemical analysis also confirms expected chemical evolution trends in the Solar neighborhood. Next, we explore the effects of stellar motion and galactic dynamics on the habitability of planets in different regions of the Galaxy. In Chapter 4, we use Gaia DR2 data to calculate 3D galactocentric velocities for stars observed by the Kepler spacecraft. We compare the velocities of confirmed Kepler host stars to those of their non-host stellar twins and find that there's no relationship between stellar velocity and planet occurrence in the Solar neighborhood. In Chapter 5, we shift our attention to the Milky Way bulge, where stars are closer together and moving more quickly on more elliptical orbits than in the disk. We simulate the orbits of bulge stars and use a semi-analytical method to derive the rate of close stellar encounters. We find that roughly 8 in 10 bulge stars will come within 1000 AU of at least 1 other star every billion years. Half of these stars experience dozens of these encounters every gigayear. These encounters can have dramatic consequences for planets, and our findings strongly suggest that the Milky Way bulge is not the most suitable environment for life. In Chapter 6, I share an overview of the science communication and outreach work I've done while in graduate school and explain how it's so closely tied to my research on GHZs.

Thesis (Ph. D.)--University of California, San Diego, 2001. / Vita. Includes bibliographical references.

Thesis (LL.M.). / Written for the Institute of Air and Space Law. Title from title page of PDF (viewed 2008/12/04). Includes bibliographical references.

Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007. / Phillip Gibbs, Committee Member ; Rick Trebino, Committee Member ; Christoph Fahrni, Committee Member ; Donald Doyle, Committee Member ; Andreas Bommarius, Committee Chair.

No description available.