Lights in Motion Observing Nearby Planets with Imaging, Wavefront Sensing, Orbital Detection, and Spectroscopy
Date
2023-09-27
Authors
Thompson, William
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Abstract
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.
Description
Keywords
Direct Imaging, Exoplanets, Wavefront Control, Spectroscopy, Orbital Modelling