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Abstract

High-contrast imaging provides an excellent tool to detect and characterise exoplanets and circumstellar disks. Understanding the connection between them is key for the improvement of planet formation and evolution theories. In this thesis, I analyse near-infrared (NIR) observations obtained with the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) to look into various stages of the evolution of planetary systems. I combine the high-contrast imaging technique with observations in the millimetre continuum, hydrodynamical simulations, and radiative transfer models, as well as atmospheric retrievals and self-consistent models to analyse and interpret the different systems. Starting with protoplanetary disks as the birthplaces of planets, I study the morphology of the disk around WaOph 6 at different wavelengths (NIR and millimetre continuum) and find the presence of spiral arms in scattered light for the first time in such a young disk. Additionally, I test the hypothesis of a planet driving the architecture of the disk through hydrodynamical simulations and radiative transfer. Moving on to more evolved systems, I first demonstrate the use of the high-contrast imaging technique to characterise companion candidates and to determine their membership to the system. Furthermore, I analyse spectro-photometric data of the exoplanet 51 Eridani b and apply an atmospheric retrieval to estimate the physical parameters of the planet, revisiting previously reported values and finding a cloud-free atmosphere. Finally, I analyse a sample of debris disks with a double belt architecture inferred via SED modelling. I present mass and location estimates of planets that may be orbiting in the gaps between the belts, as well as detection limits from the observations and plans for future research. This thesis illustrates the current challenges in our understanding of planet formation and evolution and provides possible paths to overcome them.