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.

The rapid pace of industrial growth in South Korea over the last few decades has radically altered the way people live. As the population began to shift from the countryside to the city to pursue a better life by working in manufacturing and services in lieu of agriculture, the dense urban condition began to arise as a result of this endless influx. There had been neither the time nor the technology available to take account of the occupants' comfort. Moreover, after the Korean war in 1950, many families were split apart and this caused the longing to accommodate a family together to become stronger than ever. Since the 1970's, mass production has greatly increased the availability of housing in terms of the quantity, not quality. Most new housing for the lower middle class was built as small spaces without much opportunity to enjoy interacting with neighbors or the outdoors. This study was initiated to explore the potentials of habitable spaces and to understand the importance of bringing neighborhood life back and the chance to experience nature within the constraints imposed by a limited space. As a response to the analysis of the relationship between existing housing and the city, a design element is proposed; a wall that transforms itself from a feature in an individual living space to the neighborhood and to a facet of a city. Also this study includes the investigation of different ideas and examples of using small space efficiently. / Master of Architecture

Ce travail de doctorat analyse la question du traitement de l’inventivité habitante au sein d’un bureau d’étude. L’inventivité habitante se définit par les pratiques réalisées par des habitants et détournant des normes socio-spatiales. Elles sont des modifications incrémentales et fragmentées qui participent au processus d’habitabilité. Cette thèse a pour particularité de construire un dialogue entre le monde de l’action au sein d’un bureau d’étude en aménagement du territoire et les sciences territoriales. La problématique de la thèse fait d’ailleurs référence à cet enjeu. Elle questionne la manière dont l’ingénierie territoriale a la capacité d’améliorer l’habitabilité des territoires par l’inventivité habitante.L’auteur s’appuie sur un socle théorique pragmatique et interactionniste autour des questions de l’habiter et des contraintes spatiales. Il définit l’inventivité habitante à partir d’une critique des œuvres de Michel De Certeau, notamment L’invention du quotidien, de la notion de bricolage développée par Claude Lévi-Strauss ou encore la mètis des hellénistes Détienne et Vernant. Sur les terrains d’études du cabinet de conseil, l’auteur a recherché, observé et analysé les inventivités habitantes. La profusion des terrains d’études (Communauté de Communes de Miribel et du Plateau, Aurillac, le département du Gard, etc.) a permis d’observer une grande diversité de pratiques inventives. Après une analyse quantitative, l’auteur a proposé une inventivité habitante type : des habitants se constituent en groupe(s) afin de combler un manque à l’échelle de la rue, où ni internet ni l’action publique n’ont un rôle. Ces actions s’inscrivent dans le cadre de l’économie collaborative, durant un an ou une demi-journée. Cette inventivité détourne les normes socio-spatiales en vigueur sur le territoire.A partir d’une analyse fine de l’inventivité habitante, l’auteur a travaillé sur les relations existantes avec l’habitabilité et l’ingénierie territoriale. Il affirme que l’inventivité habitante améliore l’habitabilité. Par ce postulat, il a mis en avant le processus d’émancipation comme une condition de l’habitabilité. Toute une série d’actions publiques locales ont été analysées afin d’identifier les possibilités de l’ingénierie territoriale. Enfin, l’auteur invite au débat dans un dernier chapitre, où il propose des méthodes pour une ingénierie territoriale de l’habitabilité / This Phd work analyses inhabitant inventiveness question within a planning consultant office. The inhabitant inventiveness can be defined as inhabitants practices diverting socio-spatial norms,. They are incremental and fragmented modifications which participate in the habitability process. This thesis has for distinctive characteristic to develop a dialogue between the action’s world in a design office in town planning and territorial sciences. The thesis problem underlines the stakes of such a dialogue. It questions the way territorial engineering could have the capacity to improve habitability thanks to inhabitant inventiveness.The author’s work is based on theoretical, pragmatic and interactionist theories about dwelling and spatial pressure. He defines inhabitant inventiveness from a critic of Michel De Certeau’s work, especially L’invention du quotidien, from the notion of DIY elaborate by Claude Lévi-Strauss, and mètis of the Hellenists Détienne and Vernant. From the field studies of the design office he worked for, the author looked, observed and analyzed the inhabitants inventiveness. The field studies profusion (Communauté de Communes de Miribel et du Plateau, Aurillac, le département du Gard, etc.) lead to observing a diversity of inventiveness practices. After a quantitative analysis, the author generated a model of inhabitant inventiveness : inhabitants form a group to fill a void, a “lack of”, at street level, where neither internet nor public action has no role Actions take place within the scope of collaborative economy, for one year or one half-day. This inventiveness diverts socio-spatial norms.From an in-depth analysis of inhabitant inventiveness, the author worked on the relationship between habitability and territory engineering. He claims that inhabitant inventiveness improves habitability. Local public actions were analysed to identify how spatial and territorial engineering and planning could create or restrain possibilities. Finally, the author creates a controversy in the last chapter, where he proposes methods for territorial engineering of habitability.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 166-174).

This thesis investigates how increased global mean temperatures on Earth, induced by the increase in the luminosity of the Sun as it ages, change the types of habitable environments on the planet at local scales over the next 3 Gyr. Rising temperatures enhance silicate weathering rates, reducing atmospheric CO₂ levels to below the threshold for photosynthesis, while simultaneously pushing environments past the temperature tolerances of plant and animal species. This leads to the end of all plant life and animal life (due to reduced food, O₂ and H₂O availability, as well as higher temperatures) within the next 1 Gyr. The reduction in the extent of the remaining microbial biosphere due to increasing temperatures and rapid ocean evaporation is then modelled, incorporating orbital parameter changes until all known types of life become extinct; a maximum of 2.8 Gyr from the present. The biosignatures associated with these changes are determined and the analysis extended to Earth-like extrasolar planets nearing the end of their habitable lifetimes. In particular, the stages in the main sequence evolutions of Sun-like stars within 10 pc are evaluated and used to extrapolate the stage that an Earth-analogue planet would be at in its habitable evolution, to determine the best candidate systems for a far-future Earth-analogue biosphere, highlighting the Beta Canum Venaticorum system as a good target. One of the most promising biosignatures for a microbial biosphere on the far-future Earth (and similar planets) may be CH₄, which could reach levels in the atmosphere that make it more readily detectable than it is for a present-day Earth-like atmosphere. Determining these biosignatures will help expand the search for life to the wider range of environments that will be found as the habitable exoplanet inventory grows and planets are found at different stages in their habitable evolution.

Šio magistro darbo tema yra gyvenamojo būsto rinka Lietuvos didžiuosiuose miestuose 2003- 2007 metais. Darbe nagrinėjama gyvenamojo būsto rinkos problematika: staigūs pokyčiai, šuolinis kainų ir paklausos didėjimas, pasiūlos mažėjimas, įvairūs veiksniai, įtakojantys gyvenamųjų patalpų rinką. Darbo tikslas – kelerių metų gyvenamojo būsto rinkos Lietuvoje analizė ir ateities tendencijų numatymas. Jam pasiekti darbe iškelti tokie uždaviniai: išanalizuoti gyvenamojo būsto bumo ir kainų šuolio priežastis, supažindinti su būsto paskolų įtaka gyvenamojo būsto paklausai ir prognozuoti ateities tendencijas. Darbe nagrinėjama gyvenamojo būsto ir žemės sklypų rinka: pateikiama kelerių metų šios rinkos raida bei kainų kaita Lietuvoje, rinkos bumo priežastys, tendencijos ir prognozės ateityje, pelningiausi ir paklausiausi sektoriai. / The topic of this Master’s work is the habitable accomodation market in the biggest Lithuania countries in the year 2003-2007. The paper elaborates problematic issues of the habitable accomodation market: sudden changes, increase in prices and demand, decrease in supply; as well as some factors, which influence habitable accomodation market. The paper aim is to analyse the habitable accomodation market in Lithuania for the past few years and to predict future tendencies. To reach this aim there are some tasks: it is needed to analyse the causes of the habitable accomodation boom and the price surge; to explore the influence of housing loans on the demand for habitable accomodation and to prognosticate future tendencies. The author analyses the market of the habitable accomodation and grounds: development and price alternations on this market in Lithuania for the several past years; causes of the market boom, tendencies and forecasts to the future; the most profitable and markitable sectors.

The search for extra-terrestrial life is guided by the classification of promising candidate worlds. In this classification the habitable zone acts as a measure for the perceived habitability of a circumstellar body. Habitable zone definitions vary between using a conservative and an optimistic limit. As the Sun progresses through stages of stellar evolution previously uninhabitable outer moons may receive sufficient heating for the existence of liquid water on their surface. To evaluate the possibility for life on these moons the time inside the habitable zone is calculated and compared to estimates for the time for life to develop on Earth. For these calculations the stellar evolution models of PARSEC and Dartmouth are employed. A class of moons is discovered whose time inside the habitable zone is longest during the horizontal branch evolutionary phase (fueled by helium burning in the core). Since the horizontal branch luminosity is near constant, this class is of particular interest due to being less dependent on a stabilizing climate mechanism to regulate atmospheric composition needed to counteract luminosity changes. Ultimately, it is found that regardless of moon, stellar evolution model, and habitable zone definition no post-main sequence time inside the habitable zone is as long as the time for life to arise on Earth. / <p>Research presentation</p>

Estudo das ressonâncias de três corpos na zona habitável (ZH), da estrela GJ 581 (Gliese 581), envolvendo dois planetas conhecidos e um terceiro planeta dentro da ZH. Séries de Lie são usadas para obter o Hamiltoniano médio (de segunda ordem nas massas) e teoria de Chirikov é usada para gerar um novo sistema de varáveis canônicas em que os momentos se orientam ao longo e através da ressonância. Um mapa de Hadjidemetriou é construido e permite o cálculo rápido da difusão das órbitas em uma extensa grade de condições iniciais. / Study of three-body resonances in the habitable zone (ZH), the star GJ 581 (Gliese 581), involving two known planets, and a third planet in the ZH. Lie series are used to obtain the average Hamiltonian (the second-order mass) and Chirikov theory is used to generate a new canonical variables system in which the moments are oriented along and across the resonance. A map of Hadjidemetriou is constructed and allows rapid calculation of the diffusion of orbits in an extensive grid of initial conditions.

Estudo das ressonâncias de três corpos na zona habitável (ZH), da estrela GJ 581 (Gliese 581), envolvendo dois planetas conhecidos e um terceiro planeta dentro da ZH. Séries de Lie são usadas para obter o Hamiltoniano médio (de segunda ordem nas massas) e teoria de Chirikov é usada para gerar um novo sistema de varáveis canônicas em que os momentos se orientam ao longo e através da ressonância. Um mapa de Hadjidemetriou é construido e permite o cálculo rápido da difusão das órbitas em uma extensa grade de condições iniciais. / Study of three-body resonances in the habitable zone (ZH), the star GJ 581 (Gliese 581), involving two known planets, and a third planet in the ZH. Lie series are used to obtain the average Hamiltonian (the second-order mass) and Chirikov theory is used to generate a new canonical variables system in which the moments are oriented along and across the resonance. A map of Hadjidemetriou is constructed and allows rapid calculation of the diffusion of orbits in an extensive grid of initial conditions.