Lights in Motion Observing Nearby Planets with Imaging, Wavefront Sensing, Orbital Detection, and Spectroscopy




Thompson, William

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To place our solar system into a wider context, astronomers must study a broad sample of planets around Sun-like stars in detail. This will require a combination of indirect evidence and direct imaging, which is the focus of this dissertation. Directly imaging solar system analogues is a challenging endeavour that is to a large extent, limited by our instruments and analysis techniques. This dissertation describes how some of these challenges can be overcome from many directions. First, it presents a new analysis technique that re-evaluates how we treat the problem of analyzing direct imaging data called direct signal-to-noise optimization. This approach can provide a three to five times reduction of speckle noise close to the star when applied to angular differential imaging data. Second, it presents applications of an approach for combining images in the presence of orbital motion. This removes a sensitivity limit to direct imaging caused by orbital smearing. It results in near-ideal scaling of sensitivity with square root of the number of observations. Additionally, this technique is extended to arbitrarily combine direct and indirect sources of evidence for planets. Next, this dissertation demonstrates improved instrumentation that could increase the sensitivity of future instruments. It demonstrates the Fast Atmospheric Self-Coherent Camera Technique in a laboratory environment and presents a five hundred times reduction in quasi-static speckles. It then presents a concept for an imaging Fourier transform spectrograph that could combine a self-coherent camera with high resolution spectral information at a resolution of 5,000 to 20,000. It demonstrates such an imaging spectrograph in a laboratory environment and shows how spectro-coherent differential imaging can lead to an approximately forty times reduction in speckle noise. Lastly, it describes a speculative concept for a constellation of orbital retroreflector beacons that could one day lead to the imaging of Earth-like planets from the ground. The analysis techniques developed in this dissertation are applied to a deep, targeted survey of the HR 8799 planetary system. This results in tight limits on any additional outer planets and the detection of a fifth candidate planet at just 4 AU separation, which would be one of the closest separation planets ever directly detected. These results will change how future surveys and searches for planets are completed, and ultimately contribute to understanding the Earth’s place in our local neighbourhood.



Direct Imaging, Exoplanets, Wavefront Control, Spectroscopy, Orbital Modelling