<p>Space weathering refers to the gradual spectral, microstructural, and chemical alteration of airless planetary regoliths due to their exposure to the harsh environment of outer space. Solar wind irradiation and micrometeoroid impacts are the primary space weathering processes at work in our solar system. Although the microstructural and compositional effects of space weathering are small, occurring at the sub-micron scale in individual regolith grains, their collective impact on the spectral signature of planetary surfaces is critical. Space weathering is known to change the slope, albedo, and strength of absorption band features of reflectance spectra acquired by ground- and spacecraft-based instrumentation. In this way, space weathering impedes our ability to determine planetary surface compositions from remote sensing data and pair meteorites with their parent bodies. Thanks to decades of research since the Apollo sample return missions, the planetary science community has developed a comprehensive understanding of how space weathering alters the Moon and silicate-rich asteroids. However, the effects of space weathering on primitive, carbon-rich asteroids—which dominate the outer main belt—are more poorly constrained and very complex. This dissertation aims to improve our understanding of how solar wind irradiation and micrometeoroid bombardment modifies the spectral, microstructural, and chemical properties of carbonaceous asteroidal regoliths. To accomplish this goal, this research experimentally simulates constituent space weathering processes in the laboratory on carbon-rich analog materials. A multi-faceted analytical approach including a variety of electron microscopy and spectroscopic techniques is used to probe the spectral, microstructural, and chemical changes induced by experimental space weathering.</p><p>Chapter 1 of this dissertation provides an introduction to space weathering, including a description of the current state of knowledge in the field as well as the motivation for this research. Similarly, chapter 2 provides an overview of the various experimental simulations and coordinated analytical techniques employed in this work. Chapter 3 initiates the discussion of research accomplished during this doctoral program, presenting a detailed characterization of the spectral, microstructural, and chemical effects derived from simulated solar wind irradiation of a carbonaceous asteroid analog material. More specifically, in chapter 1, I perform high flux (~1013 ions/cm2/s), high fluence (1018 ions/cm2) 1 keV H+ and 4 keV He+ irradiation experiments on the Murchison meteorite. Chapter 2 investigates the role of incident ion flux in solar wind space weathering of carbonaceous asteroidal regolith by performing a set of low flux (~1011 ions/cm2/s) and high flux (~1013 ions/cm2/s) H+ and He+ irradiation experiments on Murchison samples. These experiments are the lowest flux solar wind simulations carried out, to date. Finally, chapter 5 presents results from the first <i>combined</i> ion irradiation and heating experiments performed on a carbon-rich analog using in situ transmission electron microscopy (TEM). In situ TEM is a relatively novel technique in the planetary and geological sciences which allows users to observe the physiochemical changes caused by an external stimuli in <i>real time</i>. The experimental approach used in chapter 5 simulates both solar wind irradiation and micrometeoroid impacts, and, thus, probes the cumulative microstructural and compositional modifications induced by these concurrent space weathering processes. In chapters 3 through 5, I compare my results to previous space weathering simulations and observations of lunar and asteroidal returned samples. Findings from this dissertation advance the existing model of space weathering on carbon-rich asteroids, help inform remote sensing observations from the Hayabusa2 and OSIRIS-REx missions which have rendezvoused with C-complex asteroids Bennu and Ryugu, respectively, and provide experimental ground-truth for analyzing returned samples from these missions.</p>

Les domaines millimétrique et submillimétrique sont des domaines qui permettent de caractériser la physico-chimie des atmosphères planétaires par l'observation des molécules qui les composent. Le télescope spatial Herschel et l'interféromètre ALMA, qui entreront prochainement en service, permettront d'améliorer considérablement notre connaissance des atmosphères planétaires. L'un des principaux objectifs de cette thèse est de développer un modèle d'analyse des observations millimétriques et submillimétriques qui seront effectuées avec Herschel et ALMA. C'est en ce sens que nous détaillons un modèle qui tient compte de la géométrie sphérique des corps observés et des spécificités instrumentales propres aux télescopes utilisés. Dans un premier temps, ce qui a permis notamment de valider notre modèle de transfert radiatif, nous avons étudié l'origine des composés oxygénés dans les atmosphères des planètes géantes. Nous présentons l'analyse d'observations de Saturne et d'Uranus, effectuées avec les télescopes de l'IRAM et du JCMT, pour contraindre les sources de monoxyde de carbone dans ces atmosphères. Nous améliorons ainsi les limites supérieures précédemment publiées et réalisons la première observation du monoxyde de carbone dans l'atmosphère de Saturne dans le domaine submillimétrique. Cette observation prouve l'existence d'une source externe pour ce composé. Nous analysons également des observations récentes de Jupiter, effectuées par le télescope spatial Odin, pour contraindre l'origine externe de l'eau dans la stratosphère de cette planète. Les observations confirment que la chute de la comète Shoemaker-Levy~9 est vraisemblablement la source principale d'eau. Dans un second temps, nous avons appliqué notre modèle à l'étude de la structure thermique et la dynamique de l'atmosphère de Mars, à partir d'observations du monoxyde de carbone. Ces observations sont comparées aux prédictions d'un modèle de circulation générale, ce qui permet de vérifier la validité de ses prédictions et de fournir de nouvelles contraintes observationnelles pour ce type de modélisations. Enfin, nous avons appliqué notre modèle à l'étude des planètes géantes avec le télescope spatial Herschel, dans le cadre du programme-clé de temps garanti du télescope spatial Herschel ``Water and related chemistry in the Solar System''. Nous avons également identifié les améliorations à apporter à notre modèle pour analyser des observations ALMA. / The planetary atmospheres can be characterized by observations carried out in the millimeter and submillimeter wavelength ranges. In a near future, the Herschel Space Observatory as well as the ALMA interferometer will increase our knowledge of the planet atmospheres. One of the main goals of this thesis work consists in developping an analysis tool for millimeter and submillimeter observations, which will be carried out with Herschel and ALMA. The model we have developped takes into account the spherical geometry of the planets and the properties of the telescopes. First, we have studied the origin of oxygen compounds in the atmospheres of the giant planets. We have validated our radiative transfer model from this study. We present the analysis of observations of carbon monoxide in the atmospheres of Saturn and Uranus, which have been carried out with the IRAM and JCMT telescopes, in order to constrain the origin of this compound. We improve existing upper limits and prove the existence of an external source of carbon monoxide in the atmosphere of Saturn from the first observation of this compound at submillimeter wavelengths. We also analyse recent observations from the Odin space telescope of water vapor in the stratosphere of Jupiter to constrain its external source. We confirm that the observed water is probably mostly due to the collision of comet Shoemaker-Levy~9 with the planet. Then, we have used our model in order to study the thermal structure as well as the dynamics of the atmosphere of Mars from carbon monoxide observations. These observations are compared to predictions of a general circulation model to check the consistency of the predictions. They also provide new observational constraints to general circulation models. Finally, we have used our model to study the atmospheres of the giant planets in the frame of the Herschel garanteed time key-program ``Water and related chemistry in the Solar System''. We have also determined the upgrades to implement in our model to analyse ALMA observational data.

[Truncated abstract] This thesis examines the bonding interactions and chemical processes associated with irradiated water (H2O) and ammonia (NH3) molecules. The experiments conducted in the present study are designed to replicate the surface chemistry of outer Solar System bodies, particularly the icy surfaces of Saturn's inner moons. Infrared (IR) spectroscopy is used to identify the H2ONH3 complex isolated in an argon (Ar) matrix. An electric discharge is then applied to the H2O and NH3 species to produce the hydroxyl-ammonia (OHNH3) complex and the water-amidogen (H2ONH2) complex. Finally, the ammonia-oxygen (NH3O2) complex is formed in an Ar matrix, complementing previous studies performed by the Quickenden research group, which investigated the conversion of OH radicals into molecular O2 on icy planetary surfaces. ... An electric discharge is applied to the NH3 in Ar mixture, producing the NH2 radical subunit of the complex. Two absorption bands are assigned to the H2O subunit vibrational frequencies of the complex; at 1616.1 cm-1 for the ¿2 HOH bending fundamental and at 3532.1 cm-1 for the ¿1 OH bonded stretching fundamental. Two absorption bands are also assigned to the NH2 radical subunit vibrational frequencies of the complex; at 1498.5 cm-1 for the ¿2 HNH bending fundamental and at 3260.8 cm-1 for the ¿3 NH asymmetric stretching fundamental. These assignments are verified by the isotope substitution method, involving the formation of the deuterated D2OND2 complex analogue in an Ar matrix and the measurement of the isotope induced shifts in peak position in the IR region. The isotopic shifts displayed by the IR absorption bands are in good agreement with the theoretically calculated shifts in vibration frequency when going from the H2ONH2 complex fundamentals to the D2OND2 complex fundamentals. The theoretical calculations also derived an interaction energy of 5.2 kcal mol-1 for the HOHNH2 structure of the H2ONH2 complex. This HOHNH2 structure is also confirmed as the preferred structure of the H2ONH2 complex in the IR experiments, by the observation of a large shift in position of the absorption band associated with the H2O subunit ¿1 OH stretching fundamental, away from the position of the H2O monomer ¿1 OH stretching fundamental. This indicates that the H2O subunit donates a hydrogen for the complex bond in the HOHNH2 complex. The NH3O2 complex is identified in solid Ar matrices at 10.5 K by IR analysis. The NH3O2 complex is formed by the co-deposition of gaseous NH3 in Ar mixtures with O2 in Ar gas mixtures. An absorption band is assigned to the ¿1 OO stretching fundamental for the O2 subunit of the NH3O2 complex at 1552.0 cm-1. This assignment is verified by the isotope substitution method, involving the formation of the deuterated ND3O2 complex analogue in an Ar matrix and the measurement of the isotope induced shift in peak position in the IR region. The isotopic shift displayed by the IR absorption band is in good agreement with the theoretically calculated shift in vibration frequency when going from the NH3O2 complex fundamental to the ND3O2 complex fundamental. The theoretical calculations also derived an interaction energy of 0.28 kcal mol-1 for the NH3O2 complex.

Cette thèse considère quatre systèmes physiques complexes pour lesquels il est exceptionnellement possible d’identifier des variables lentes qui contrôlent l'évolution à temps long du système complet. La séparation d'échelle de temps entre ces variables lentes et les autres variables permet d'utiliser la technique de moyennisation stochastique pour obtenir une dynamique effective pour les variables lentes. Cette thèse considère la possibilité de prédire les événements rares dans le système solaire. Nous avons étudié deux types d’événements rares. Le premier est un renversement possible de l'axe de rotation de la Terre en l'absence des effets de marée de la Lune. Le second est la désintégration de l'ensemble du système solaire interne suite à une instabilité dans l'orbite de Mercure. Pour chacun des deux problèmes, il existe des variables lentes non triviales, qui ne sont pas données par des variables physiques naturelles. La moyennisation stochastique a permis de découvrir le mécanisme physique qui conduit à ces événements rares et de donner, par une approche purement théorique, l'ordre de grandeur de la probabilité de ces phénomènes. Nous avons également montré que la déstabilisation de Mercure sur un temps inférieur à l'âge du système solaire obéit à un mécanisme d'instanton bien décrit par la théorie des grandes déviations. Le travail effectué dans cette thèse ouvre donc un nouveau champ d'action pour l'utilisation d'algorithmes de calcul d'événements rares. Nous avons utilisé pour la première fois les théorèmes de moyennisation stochastique dans le cadre de la mécanique céleste pour quantifier l'effet stochastique des astéroïdes sur la trajectoire des planètes. Enfin, une partie du travail porte sur un problème de turbulence géophysique: dans l'atmosphère de Jupiter, on peut observer des structures zonales (jets) à grande échelles évoluant beaucoup plus lentement que les tourbillons environnants. Nous montrons qu'il est pour la première fois possible d'obtenir explicitement le profil de ces jets par moyennisation des degrés de liberté turbulents rapides. / The present thesis describes four complex dynamical systems. In each system, the long-term behavior is controlled by a few number of slow variables that can be clearly identified. We show that in the limit of a large timescale separation between the slow variables and the other variables, stochastic averaging can be performed and leads to an effective dynamics for the set of slow variables. This thesis also deals with rare events predictions in the solar system. We consider two possible rare events. The first one is a very large variation of the spin axis orientation of a Moonless Earth. The second one is the disintegration of the inner solar system because of an instability in Mercury’s orbit. Both systems are controlled by non-trivial slow variables that are not given by simple physical quantities. Stochastic averaging has led to the discovery of the mechanism leading to those rare events and gives theoretical bases to compute the rare events probabilities. We also show that Mercury’s short-term destabilizations (compared to the age of the solar system) follow an instanton mechanism, and can be predicted using large deviation theory. The special algorithms devoted to the computation of rare event probabilities can thus find surprising applications in the field of celestial mechanics. We have used for the first time stochastic averaging in the field of celestial mechanics to give a relevant orders of magnitude for the long-term perturbation of planetary orbits by asteroids. A part of the work is about geophysical fluid mechanics. In Jupiter atmosphere, large scale structures (jets) can be observed, the typical time of evolution of which is much larger than that of the surrounding turbulence. We show for the first time that the mean wind velocity can be obtained explicitly by averaging the fast turbulent degrees of freedom.

Made available in DSpace on 2014-12-17T14:57:40Z (GMT). No. of bitstreams: 1 RaimundoNAC.pdf: 846914 bytes, checksum: 05f5ca2a386c7e7ce11ac1dae42ab71d (MD5) Previous issue date: 2007-06-01 / An solar alternative system for water heating is presented. Is composed for one low cost alternative collector and alternative thermal reservoir for hot water storing. The collector of the system has box confectioned in composite material and use absorption coils formed for PVC tubes. The box of hot water storage was confectioned from a plastic polyethylene drum used for storage of water and garbage, coated for a cylinder confectioned in fiber glass. The principle of functioning of the system is the same of the conventionally. Its regimen of work is the thermosiphon for a volume of 250 liters water. The main characteristic of the system in considered study is its low cost, allowing a bigger socialization of the use of solar energy. It will be demonstrated the viabilities thermal, economic and of materials of the system of considered heating, and its competitiveness in relation to the available collectors commercially. Relative aspects will be boarded also the susceptibility the thermal degradation and for UV for the PVC tubes. It will be shown that such system of alternative heating, that has as main characteristic its low cost, presents viabilities thermal, economic and of materials / Apresenta-se um sistema de aquecimento solar de ?gua, trabalhando em regime de termossif?o, constitu?do por um, coletor solar alternativo e um reservat?rio armazenador de ?gua tamb?m alternativo. O coletor foi constru?do com um material comp?sito a base de gesso e isopor e o reservat?rio t?rmico a partir de um tambor de polietileno de 200 litros utilizado para armazenamento de ?gua e lixo recoberto por um cilindro em fibra de vidro, tendo isopor triturado entre as duas superf?cies. A utiliza??o do comp?sito e a nova forma de obten??o da grade absorvedora permitem que o coletor apresente apenas tr?s elementos ao inv?s dos cinco caracter?sticos de um coletor convencional, diminuindo, portanto o seu custo. A superf?cie absorvedora dos coletores foi montada utilizando-se tubos de PVC pintados de preto fosco, ligados atrav?s de uma configura??o em paralelo, utilizando como elementos de liga??o conex?es em T de PVC de mesmo di?metro. Ser?o apresentados dados de efici?ncia e perda t?rmicas que demonstram a efici?ncia t?rmica do sistema de aquecimento proposto Abordarse-? tamb?m aspectos relativos a susceptibilidade de degrada??o dos tubos de PVC quando expostos a radia??o solar. Mostrar-se-? que tal sistema de aquecimento alternativo, que tem como principal caracter?stica seu baixo custo, apresenta viabilidades t?rmica, econ?mica e de materiais

Made available in DSpace on 2014-12-17T14:57:43Z (GMT). No. of bitstreams: 1 NatanaeyfleRGS.pdf: 3490813 bytes, checksum: f204addb5db220050260ffb91221e262 (MD5) Previous issue date: 2008-02-08 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / A solar alternative system for water heating is presented. It work on a thermosiphon, consisting of one or two alternative collectors and a water storage tank also alternative, whose main purpose is to socialize the use of energy mainly to be used by people of low income. The collectors were built from the use of pets bottles, cans of beer and soft drinks and tubes of PVC, ? " and the thermal reservoirs from a drum of polyethylene used for storage of water and garbage placed inside cylinder of fiber glass and EPS ground between the two surfaces. Such collectors are formed by three elements: pet bottles, cans and tubes absorbers. The heating units, which form the collector contains inside the cans that can be closed, in original form or in the form of plate. The collectors have an absorber grid formed by eight absorbers PVC tube, connected through connections at T of the same material and diameter. It will be presented data of the thermal parameters which demonstrate the efficiency of the heating system proposed. Relative aspects will be boarded also the susceptibility the thermal degradation and for UV for the PVC tubes. It will be demonstrated that this alternative heating system, which has as its main feature low cost, presents thermal, economic and materials viabilities / Apresenta-se um sistema de aquecimento de ?gua solar atrav?s do uso da energia solar, trabalhando em regime de termossif?o, constitu?do por um ou dois coletores, coletores alternativos e um reservat?rio armazenador de ?gua tamb?m alternativo, cuja principal finalidade ? socializar o uso da energia principalmente para ser utilizada por popula??es de baixa renda. Os coletores foram constru?dos a partir da utiliza??o de garrafas pet, latas de cervejas e refrigerantes e tubos de PVC de ? e os reservat?rios t?rmicos a partir de um tambor de polietileno utilizado para armazenamento de ?gua e lixo colocado no interior de cilindro em fibra de vidro, tendo isopor triturado entre as duas superf?cies. Tais coletores s?o formados por apenas tr?s elementos: garrafa pet, latas e tubos absorvedores. As unidades de aquecimento que formam o coletor cont?m em seu interior as latas que podem estar fechadas, vazadas ou em forma de aletas. Os coletores possuem uma grade absorvedora formada por oito tubos absorvedores de PVC, ligados atrav?s de conex?es em T do mesmo material e di?metro. Ser?o apresentados dados de rendimento e perda t?rmicos que demonstram a efici?ncia do sistema de aquecimento proposto Abordar-se-? tamb?m aspectos relativos a susceptibilidade de degrada??o dos tubos de PVC quando expostos a radia??o solar. Mostrar-se-? que tal sistema de aquecimento alternativo, que tem como principal caracter?stica seu baixo custo, apresenta viabilidades t?rmica, econ?mica e de materiais

This work concerns the research and application of data visualization techniques to depict ongoing activities in mankind’s investigation of space as part of a larger open-source visualization- and science-outreach software known as OpenSpace. It involves the construction of a physically accurate virtual environment of our local star group and solar system so as to facilitate development of a robust and generalized solution capable of articulating mission-science to its viewers. The research part is focused on deploying data visualization methods suitable for contextualizing scientific findings towards the general public in a pedagogical manner, with the end goal to provide a fully operational New Horizons visualization on the day of encounter with Pluto for the first public broadcast of OpenSpace across the globe.

Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-08-09T11:18:45Z No. of bitstreams: 1 sebastiaomaurofilho.pdf: 637836 bytes, checksum: 0629945b7a9ce79385454dd5fb18c92f (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-08-09T13:36:52Z (GMT) No. of bitstreams: 1 sebastiaomaurofilho.pdf: 637836 bytes, checksum: 0629945b7a9ce79385454dd5fb18c92f (MD5) / Made available in DSpace on 2017-08-09T13:36:52Z (GMT). No. of bitstreams: 1 sebastiaomaurofilho.pdf: 637836 bytes, checksum: 0629945b7a9ce79385454dd5fb18c92f (MD5) Previous issue date: 2017-01-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese aplicamos o método perturbativo, em nível clássico, à Gravidade de Quarta Ordem e à Relatividade Geral estendida pelo Grupo de Renormalização (RGGR). Para explorar as perturbações métricas, na teoria da Gravidade de Quarta Ordem, nós usamos a formulação de campos auxiliares para uma métrica de fundo curva e arbitrária. O caso em que a métrica de fundo é Ricci-plano foi elaborada em detalhes. Notamos que o uso de campos auxiliares tornará a análise perturbativa mais simples e os resultados mais claros. Como uma aplicação, nós reconsideramos os resultados para a estabilidade do buraco negro de Schwarzschild e discutimos alguns avanços para o buraco negro de Kerr na Gravidade de Quarta Ordem. Nós também usamos o método perturbativo para explorar os limites newtoniano e pós-newtoniano de RGGR. No Sistema Solar, RGGR depende de um único parâmetro adimensional /9, e ele é tal que para /9 = 0 a Relatividade Geral é obtida. Para estudar o limite newtoniano fizemos uso da técnica de transformação conforme e da dinâmica do vetor de Laplace-Runge-Lenz (LRL). Isso nos permitiu estimar o limite superior de P dentro do Sistema Solar em dois casos: um quando é levado em conta o efeito de potencial externo e outro quando ele não é considerado. Anteriormente, foi encontrado que este parâmetro satisfaz o seguinte limite /9 < 10-21, quando o efeito de potencial externo é ignorado. Entretanto, como nós mostramos esse limite cresce cinco ordens de magnitude P < 10-16 quando tal efeito é considerado. Além disso, mostramos que para um certo limite, RGGR pode ser facilmente testada usando o formalismo parametrizado pós-newtoniano (PPN). / In this thesis we applied the perturbative method, on a classical level, to the fourth-order gravity and the Renormalization Group extended General Relativity (RGGR). We will consider auxiliary fields formulation for the general fourth-order gravity on an arbitrary curved back-ground to analyze the metric perturbations in this theory. The case of a Ricci-flat background was elaborated in detail. We noticed that the use of auxiliary fields helps to make the pertur-bative analysis easier and the results more clear. As an application we reconsider the stability problem of the Schwarzschild and Kerr black holes in the fourth-order gravity. We also used the perturbative method to develop the Newtonian and post-Newtonian limits of RGGR. In the Solar System, RGGR depends on a single dimensionless parameter 0, and this parameter is such that for 0 = 0 one fully recovers General Relativity in the Solar System. In order to study the Newtonian limit we used the conformal transformation technique and the dynamics of the Laplace-Runge-Lenz vector (LRL). In this way, we could estimate the upper bound for 0 within the Solar System in two case: the case where the external potential effect is considered and the another when it is not considered. Previously this parameter was constrained to be 0 < 10-21, without considering the external potential effect. However, as we showed, when such an effect is considered this bound increases by five orders of magnitude, O < 10-16. Moreover, we showed that under a certain approximation RGGR can be easily tested using the parametrized post-Newtonian (PPN) formalism.

La détection et la caractérisation d'exoplanètes apparaissent clairement comme des thèmes centraux de l'observation astronomique pour les années à venir. Les projets spatiaux ou au sol sont nombreux (HARPS, CoRoT, Kepler, JWST, SPHERE...), mais les études théoriques visant à l'analyse et à la compréhension des données recueillies et à venir sont nécessaires. Durant cette thèse j'ai étudié divers processus physiques affectant la structure interne et l'évolution des planètes géantes, aussi bien au sein, qu'à l'extérieur de notre système solaire. J'ai notamment modélisé en détail: -L'impact de l'irradiation intense émise par l'étoile sur l'atmosphère d'une planète à faible distance orbitale, et l'effet induit sur l'évolution interne de cette planète. -Le couplage par dissipation de marée de l'évolution orbitale et thermique d'une planète interagissant avec sa proche étoile parente. -L'effet de la déformation due aux marées sur les paramètres observables d'une planète en transit grâce au suivi photométrique de son passage devant l'étoile. -L'incidence sur la structure et l'évolution d'une diminution de l'efficacité du transport de chaleur par convection due à un gradient d'éléments lourd dans l'enveloppe gazeuse d'une planète géante, conduisant au phénomène de convection double-diffusive. A travers l'étude des ces divers processus, j'ai développé différents modèles analytiques et codes numériques qui sont à la fois flexibles et robustes, et qui permettent maintenant d'étudier certaines propriétés des nouveaux objets substellaires détectés à mesure qu'ils sont découverts. / The detection and characterization of extrasolar planets clearly appears as one of the main goals of observational astronomy for the coming years. Space and ground project are numerous, but theoretical studies aimed at analyzing and understanding available and future data are needed. During this thesis, I study various physical processes affecting the internal structure and evolution of both solar, and extrasolar giant planets. In particular I investigate : -the impact of the intense stellar irradiation received by a close in planet on its subsequent internal evolution. This allows me to quantify the radius anomaly of bloated Hot Jupiters and to constrain their internal composition. -the tidal and centrifugal distortion of a fluid planet. By using both analytical and numerical models, I show how non-sphericity of the planet affects transit measurements, yielding an underestimation of its radius. -how the presence of double-diffusive convection caused by a heavy elements gradient in the gaseous envelope of a planet can decrease the efficiency of its internal heat transport, and affect its structure and evolution. -the coupling between the orbital and the thermal evolution of a planet arising from the strong star-planet tidal interaction. Subsequently, I find that tidal heating alone is not a viable explanation for the observed radius anomaly of transiting planets. Through these different studies, I developed various analytical models and numerical codes that are both flexible and robust, and which now allow one to study the properties of new extrasolar planets and brown dwarfs as they are discovered.

Les particules cométaires sont des témoins de l’évolution du système solaire, dont les caractéristiques peuvent être estimées à partir de la lumière qu’elles diffusent et émettent.<p>Je montre qu’un modèle de diffusion lumineuse par un nuage d’agrégats fractals et de sphéroïdes permet d’interpréter, en fonction de la distribution en taille et des matériaux constitutifs, des observations polarimétriques en angle de phase et longueur d'onde. Le modèle est en particulier appliqué à la comète Hale-Bopp, et au milieu interplanétaire en modélisant aussi les observations thermiques.<p>Je développe des outils de diffusion lumineuse (numériques et expérimentaux) pour analyser des agrégats analogues aux particules protoplanétaires qui seront formés avec ICAPS à bord de l’ISS. De façon complémentaire, une simulation expérimentale en vol parabolique avec PROGRA2 me permet de déterminer les propriétés physiques de microparticules d’intérêt astrophysique par des mesures polarimétriques.<p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished