One of the key discoveries in exoplanet research over the past decade is the abundance of small planets in our Milky Way. Despite their high numbers, our understanding of their atmospheres remains... Show moreOne of the key discoveries in exoplanet research over the past decade is the abundance of small planets in our Milky Way. Despite their high numbers, our understanding of their atmospheres remains limited, and it is unknown if they possess atmospheres at all. Predicting the presence of an atmosphere on small planets is challenging due to factors like atmospheric escape and volcanism. Reliable determination requires direct study of thermal emission, reflected light, or transmission spectrum. With the launch of the JWST in late 2021, we gained unprecedented access to detailed observations of rocky exoplanets, enabling the search for atmospheres composed of carbon dioxide, oxygen, and nitrogen on temperate rocky worlds. My thesis summarizes my work on atmospheric characterization of small, rocky exoplanets using space-based telescopes such as Spitzer, Hubble, and JWST. I have studied a wide temperature range, from lava worlds with atmospheres of outgassed rock vapor at over 2000 Kelvin, to terrestrial planets with temperatures around 400 Kelvin, similar to our inner solar system. I characterized the surfaces and atmospheres of exoplanets like K2-141 b and TRAPPIST-1 c to ultimately learn about their surfaces and the conditions under which rocky planets can retain atmospheres. Show less
Over the last three decades, the discovery of exoplanets has revealed the boundless variety of worlds beyond our own Solar System. Majority of planetary systems contain short-period planets that... Show moreOver the last three decades, the discovery of exoplanets has revealed the boundless variety of worlds beyond our own Solar System. Majority of planetary systems contain short-period planets that are larger than Earth but smaller than Neptune. For rocky planets, the strong irradiation causes the surface to melt, forming dayside oceans of molten silicates. These are known as lava worlds. From a theoretical standpoint, lava worlds are expected to outgas silicate-rich atmospheres, which can be characterised using spectroscopy techniques. Spectroscopy allows astronomers to single out a multitude of chemical species in exoplanets, and with the James Webb Space Telescope (JWST), it is now possible to characterise even rocky planets.To reinforce our understanding of distant worlds it is critical that we can reproduce the observed results using computational models. A variety approaches exist, however due to their flexibility and adaptability, using averaged 1-D models is prefered. The work in this thesis heavily focuses on using 1-D chemistry and radiative-transfer codes to simulate atmospheres of super-Earths and sub-Neptunes, including volatile and silicate-rich compositions. The main goal is to guide observers to potentially detectable species that would help us gain insight into many of the drawn assumptions. The research done indicates a multitude of detectable species such as HCN, CN, CO, SiO, and SiO2. Models also show that silicate atmospheres are plagued with deep temperature inversions, strongly affecting observability. Most of the presented results are especially applicable to low-resolution infrared spectroscopy for observations with JWST. Show less
