Investigating the characterisation of exoplanet atmospheres through retrieval with advanced chemistry modelling
Bieger, MF
Date: 20 May 2024
Thesis or dissertation
Publisher
University of Exeter
Degree Title
PhD in Astrophysics
Abstract
Exoplanet science concerns itself with questions surrounding these planets around other stars, in an attempt to narrow down on the questions that humanity have been grappling with since time immemorial: how did we get here?
This thesis focuses on the questions of these planet's atmospheres. What are planet atmospheres composed of? ...
Exoplanet science concerns itself with questions surrounding these planets around other stars, in an attempt to narrow down on the questions that humanity have been grappling with since time immemorial: how did we get here?
This thesis focuses on the questions of these planet's atmospheres. What are planet atmospheres composed of? What kind of chemistry occurs in these atmospheres?
Attempting to answer these questions is done through both observing and modelling. As a planet revolves around its host star, light from the host star passes through the planet's atmosphere. With both ground-based and space-based telescopes, we can capture this light with spectroscopic instruments. Spectroscopy takes advantage of molecules' inherent quantum properties to enable us to discern how molecules are being either absorbed or scattered by the planet's atmosphere.
Forward models are able to build up a picture of a planet's atmosphere by approximating the radiation from host star down through layers of the atmosphere. Retrievals combine these with observations; and iterate over the forward models in order to attempt to match a forward model to the spectra.
In this work, we use the ATMO forward model, and the retrieval tools PARC and TauREx 3.1. We incorporate ATMO chemistry into the TauREx 3.1 architecture as a plugin called frogr, as well as create an additional parameter pressure-temperature profile called MadhuSeager2009. We use these tools to examine the properties of one archetype of exoplanets known as hot Jupiters.
With the development of these additional tools, we are able to provide a more physically and chemically informed picture of the thermal structure and chemistry of these alien atmospheres. This will go on to strengthen the arsenal of the observer's toolboxes as telescopes such as JWST and ARIEL provide more high quality spectra of various planets.
Doctoral Theses
Doctoral College
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