In this thesis, I present three main results which demonstrate significant development in the field of exoplanet atmosphere detection and modelling. A model for estimating the distortion of hot-Jupiter exoplanets due to the gravitational attraction by the host star solely based on observable parameters of transiting systems. The most significant case of distortion is that of the exoplanet WASP-12b which shows a bulk density over-estimation of 12%. In order to investigate the systematic sources of error associated with ground-based observations, the secondary eclipse of the transiting hot- Jupiter WASP-19b was observed, and found to have an eclipse depth of O.88±O.19mmag based on a single observation. Whilst this does represent a significant result, the systematics present in the data support further observations to better constrain the depth, duration and timing of the secondary eclipse. The final result presented in this thesis is a pilot study of the technique of 'defocussed transmission spectroscopy', a method of observation which is designed to allow for the detection of elements in the atmospheres of transiting extra-solar planets from groundbased platforms. I present limits on the detectability of sodium in exoplanet atmospheres, and provide a detailed investigation into the systematics associated with this novel observing technique. I also make recommendations as to how future observations can be improved, and present a possible detection of sodium in the atmosphere of WASP-12b with an absorption depth of O.12±O.03%.

Astrophysical noise poses a severe stumbling block on the pathway to the radial velocity confirmation of habitable Earth-like worlds. In particular, photospheric magneto-convection sets a fundamental limitation on the obtainable radial velocity precision. Consequently, in this thesis, I develop a multi-component parameterisation of granulation that can be used to reconstruct stellar line asymmetries and radial velocity shifts due to photospheric convective motions across the stellar disc. The parameterisation consists of four components: granules, magnetic and non-magnetic intergranular lanes, and magnetic bright points. These components are constructed by averaging Fe I 6302 A line profiles output from detailed radiative transport calculations of the solar photosphere. Each of the four categories adopted are based on magnetic field and continuum intensity limits determined from examining three dimensional magnetohydrodynamic simulations with an average magnetic flux of 200 G. I demonstrate that, on average, these four components can accurately reconstruct granulation produced from modelling 12 x 12 Mm2 areas on the solar surface, to better than ~ ± 20 cm s-'. I also establish the applicability of this parameterisation across magnetic stellar activity levels by 'successfully reconstructing profiles from a 50 G simulation. This parameterisation is then used to construct Sun-as-a-star observations to identify how the convective plasma motions on the stellar surface alter the disc-integrated profiles. I find that the velocity asymmetry (a measurement comparing the spectral information content of the blue wing to the red wing) and brightness measurements are the best-suited diagnostics for reducing granulation noise to a level sufficient for the confirmation of habitable, terrestrial-mass planets. In addition, I identify a potential new source of astrophysical noise, and establish tentative links between photometric variability and radial velocity variations in quiet stars; both of which are important steps on the pathway to Earth-like alien worlds.

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Newly formed planetary systems are very challenging to observe with traditional methods. The dusty environment around young planet-hosting star systems either reduces the sensitivity of measurements (requiring a longer integration time) or renders techniques such as transit observations impossible. Therefore, this thesis aims to determine a set of markers that , if present in a system, increase the likelihood that said system is hosting a young planet. Using these markers to target observations towards promising candidates only, the best use of instrumentation can be made, and the probability of a positive detection increased. In this work N-body simulations of planetesimal disks were conducted, the creation of collisional second generation dust is modelled in two different ways (statistically and directly), and observability studies are performed for each case. Of the two different sets of simulations presented, each consists of a control simulation (only planetesimals) and the main simulations (a planetesimal disk with an embedded Jupiter mass planet). A model for the velocity field of fragments from collisions between planetesimals was also constructed. Synthetic images of the direct set of numerical simulations show a bright double-ring structure in the case of a low eccentricity planet , whereas a high eccentricity planet would produce a characteristic inner ring with accompanying disk asymmetries when compared to the control cases. The statistical simulations also show a double ring for a low eccentricity planet and disk asymmetries for a high eccentricity planet, but no inner ring is observed in the eccentric case. The strongest marker we can establish is a bright double ring, which would indicate the presence of a low eccentricity planet. In a system where primordial dust has been depleted by an order of magnitude with respect to a protoplanetary disk (i.e. a transitional disk) , observations with ALMA would be able to detect the structure.

The discovery of nearly two thousand extrasolar planets over the last two decades is indicative that planets form everywhere. Exoplanet detections have been made of a plethora of planetary types and sizes across a wide range of orbital characteristics. One of the more exotic locations that planets have been discovered in is around stellar binaries. Their proximity to such a large time-dependent potential from the orbital motion of the stars can be problematic for their formation and long-term stability. Circumbinary planets, with orbits that fully encompass the binary, have been found to orbit as close as 0.3 au to the binary barycenter and are thus subject to strong gravitational perturbations. In the formation stage, the circumbinary protoplanetary disk experiences interactions with the binary which significantly alters the dynamics and hence collisional evolution of planetesimals which struggle to grow into the planets we see. To answer the question: Could observed circumbinary planets have formed in-situ? we perform a combination of N-body, hydro dynamical and subsequently hybrid simulations to investigate the feasibility of planet growth under these conditions. Our initial N-body simulations are performed in association with an advanced collision model to identify locations in the disk where planetesimals can accrete. We perform hydro dynamical simulations of circumbinary gas disks to investigate the structure and evolution of a fluid in response to a binary, across a wide range of fluid parameters. The resulting data, a quasi-steady-state surface density profile, is integrated in a semi-analytical way to account for gas feedback on planetesimals. Our work suggests that the majority of observed closely-orbiting circumbinary planets could not form in-situ due to an overwhelming number of erosive collisions caused by high impact velocities originating from the planetesimals' dynamical interaction with the binary and gas gravity. Planetary embryos must have formed further out in the disk, where velocities are lower, and this result indicates that migration is a necessary component of planetary evolution in these systems.

Hot Jupiter exoplanets are a previously unknown and fascinating field of study. Models of planet formation based only around the Solar System did not predict their existence, occupying as they do the orbital region less than 0.1 AD from their parent stars. Believed to be tidally locked, always presenting the same face to the star, these gas giants are bathed in intense irradiation, and inhabit a regime alien to anything known in the Solar System. As exoplanetary surveys discover an increasing number of planets, the ubiquity of hot Jupiters in the galaxy continues to be confirmed. Both the evolution and the atmospheric dynamics of these unusual planets are natural focuses of study. However, most authors have historically concentrated on one or the other of these two lines of enquiry, although both are linked. In the case of gas giants in particular, which have no true ground or otherwise easily defined surface layer, the two regimes blend towards the outer layers of the planet. This convergence renders the possibility of model overlap ever more relevant, a possibility that is here studied, both independently and together, ultimately continuing to the modelling of the specific known exoplanets HD 209458b, HD 189733b, and WASP-7b. It is found that, while it is reasonable for interior evolution model results to be used to provide boundary conditions and atmospheric characteristics for the purposes of three-dimensional atmospheric modelling, the reverse is a much more difficult propo- sition, providing few truly relevant constraints. Observational characteristics are also predicted, with cyclic variability found in the case of HD 209458b, a more permanently variable state in the case of HD 189733b, and very little longitudinal temperature variation for the calmer atmosphere of WASP-7b.

Calcium-Aluminium-rich inclusions (CArs) are the first solids to form in the early Solar System. They are oftensurrounded by Wark-Lovering (WL) rims, composed of sequential mineral layers, that offer a record of the conditions during the earliest stages of Solar System evolution, just after CAi formation. Analyses of oxygen and magnesium isotopes in nine CAIs and their WL rims selected in CO, CR, and CV chondrites, displaying different alteration histories, permit an investigation of the evolution of 0 isotope compositions in the early Solar System, and the processes that caused it.