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
More than 5,000 exoplanets have been found over the past couple of decades. These exoplanets show a tremendous diversity, ranging from scorching hot Jupiters, common super-Earths, to widely... Show moreMore than 5,000 exoplanets have been found over the past couple of decades. These exoplanets show a tremendous diversity, ranging from scorching hot Jupiters, common super-Earths, to widely separated super-Jupiters on the planet/brown dwarf boundary. We have now moved into the era of exoplanet atmospheric characterisation. Two crucial techniques for characterizing these exoplanets from the ground are high-contrast imaging and high-resolution spectroscopy. In the first part of the thesis, existing facilities are used to characterize the atmospheres of two of the most accessible types of planets: An ultra-hot Jupiter (WASP-76b) and a young supter-Jupiter (beta Pictoris b). The second part of the thesis develops instrumental concepts that are required to push exoplanet characterization towards smaller and closer-in planets. It shows how we can choose between spectral resolution, bandwidth, and field-of-view in developing an instrument for exoplanet detection, and how one can design an nearly optimal wavefront sensor for adaptive optics. Finally, it is demonstrated how machine learning techniques can help us improve the performance of these adaptive optics systems such that we can reach deeper contrasts for exoplanet imaging and characterization. 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
Casasayas Barris, N.; Orell-Miquel, J.; Stangret, M.; Nortmann, L.; Yan, F.; Oshagh, M.; ... ; Sedaghati, E. 2021
We invite you to join us on a walk through the newsroom of a regional newspaper, Dagblad van het Noorden. We trace how the journalists perceive, articulate, engage, embrace, challenge, are... Show moreWe invite you to join us on a walk through the newsroom of a regional newspaper, Dagblad van het Noorden. We trace how the journalists perceive, articulate, engage, embrace, challenge, are receptive to, and give form to the ‘atmospheres’ of their workspace. The concept of atmospheres is central in how we have looked at the newsroom. On this walk, we explore the spatial, socio-cultural, rhythmic, tonal, and somatic characteristics of the recently redesigned newsroom, using video, sound, text, and drawing. Employing artistic methods, we want to let you experience this newsroom together with us – giving you insight into the journalists’ lived experience of their profession as fundamentally interwoven with the idiosyncrasies of their workspace. Our host on the walk is online news editor Alfred Meester. Alfred walked us, Saskia and Sander, through the newsroom, which we visited as part of the project Exploring Journalism’s Limits (funded by the Dutch Research Council, NWO, project number: 314-99-205). Also joining us on this day is Ricky Booms, a visual artist invited to reflect on the space alongside us. Along the way, we encounter visual editors, interns, freelancers, editorial staff writers, and learn about the kinds of spaces that resonate with them. The walk takes approximately 45 minutes. Show less
The thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants,... Show moreThe thesis "Spinning Worlds" is about the characterisation of two types of gas-giant exoplanets: Hot Jupiters, with orbital periods of fewer than five days, and young, wide-orbit gas giants, with orbital periods as long as thousands of years. The thesis is based on near-infrared observations of 1 hot Jupiter and 3 wide-orbit gas giants at high spectral resolution. The observing strategies and the analyses are unique for the two types. For the hot Jupiter, HD 209458 b, the focus is the vertical temperature structure of the atmosphere. This particular hot Jupiter was previously thought to have an atmospheric layer where the temperature increases with altitude, but we found evidence against the existence of such a layer. The three wide-orbit gas giants are all in the early stages of their lives, and we measured their rotation and found a correlation with age: The very youngest objects rotate more slowly than the slightly older (20 million years) objects. We interpret this as the initially hot and bloated exoplanets cooling down and contracting, causing them to spin-up, until the contraction slows down as they approach a radius comparable to that of Jupiter. Show less
This thesis presents observations of exoplanets orbiting very close to their parent star, with a particular focus on a novel technique for characterizing their atmospheres. This is based on the use... Show moreThis thesis presents observations of exoplanets orbiting very close to their parent star, with a particular focus on a novel technique for characterizing their atmospheres. This is based on the use of high-resolution spectroscopy from the ground. The first detection of the atmosphere of a non-transiting planet is presented, together with the determination of its mass and orbital inclination. Moreover, it is shown that high-dispersion spectroscopy is very effective in recognizing molecular species, measuring their relative abundances, and determining whether temperature increases or decreases with altitude in the observed planetary atmospheres. The method also led to the measurement of the rotational period of a transiting exoplanet, which was found to be tidally locked, in line with theoretical predictions. Finally, the evidence for the disintegration of a small, rocky planet candidate in the Kepler database is presented. This result was obtained by fitting the light curve of the object with a model of a trailing tail of dust. Show less
