Teaching & Outreach

In this thesis, trajectories of particles within an Hot Jupiter atmosphere were simulated using data of GCM simulations while considering changing size of the particles due to changes in the cloud particle properties inside the atmosphere. The results show that there are three well defined regions in terms of altitude, pressure and temperature inside the atmosphere. Particle trajectories are defined by the regions in the atmosphere where particles are either created (> 5.000.000m), evaporated (< 3.500.000m) or mostly reside in large clouds. A cloud dominated region was spotted between 3.500.000m and 4.500.000m altitude. In lower altitude layers possible low pressure areas with resulting strong updrafts, downward trajectories for evaporating particles and gyres were identified. Particle trajectories at high altitudes have a strong correlation to gas temperature distribution. This is caused by Rossby waves because of the rotation of the exoplanet featuring hot and cold spots in the atmosphere.

This bachelor thesis studied how a simplification of the nucleation process for TiO2 is affecting the formation of CCNs. For this purpose, a closed kinetic nucleation approach was used, making several assump- tions. TiO2, being highly reactive and relatively easy to model, was chosen to be the only nucleation species. The cluster formation was studied for a homomolecular polymer growth up to a maximum size of N = 10 and for the temperature range of effective TiO2-cluster formation T = 400, . . . , 1000 K. Reduced networks show a shift of a few hours in time in the first simulation days and a shift in the magnitude of nCP , after it converged to a constant value. In order to minimize these shifts, four of the least deviating networks were combined to create 11 new networks using 12 to 24 reactions. It was achieved to keep the shift in the long-term magnitude below 0.02 for all temperatures using a combined network of 18 reactions. Thus, simplifications in the cluster formation process can be performed with low effects on the long-term values of nCP . In contrast, time shifts are connected with the number of reactions and therefore the computational costs.

This report investigates the size dependence of cloud particles advecting in a Hot Jupiter atmosphere and the behaviour of cloud particles (of varying sizes) based on the initial conditions of the cloud particle system using Hot Jupiter GCM simulations. Depending on the sensitivity degree of the initial conditions of the system, the system can be termed as chaotic if the Lyapunov exponent is a positive integer. We calculate the drag force of the gas particle and the equilibrium drift velocity of the cloud particle for a given set of cloud particle radii using hydrodynamic equations. We, then, obtain Lyapunov spectra between the same set of cloud particle radii and find that the system shows a small chaotic behaviour. A correlation between the results can be established using Pearson’s correlation method. Understanding the degree of chaos in a cloud particle system being advected in Hot Jupiters can help us model turbulence in climate and atmosphere models of Hot Jupiters more accurately.

Using a chemical network to model exoplanet atmospheres based on temperature, pressure and initial conditions, the dynamic of the atmosphere as well as quantities of four key molecules (H2O, CH4 , CO2 and O2 ) were studied. The impact of different temperatures, pressures, humidity and nature of the composition were the focus of this project. Comparing simulated Mars atmosphere and Venus atmosphere with empirical data proved the used simplified model effective. The model fails for earth-like planets that include more complex atmospheric chemistry most likely due to the presence of biochemistry.

Exoplanet transits have proven to be a powerful tool to detect exoplanets. With ever better instrumentation, we start to get more insides into their atmospheres. One important factor in the observations are clouds. Their large opacities in the visible wavelengths mute most atomic and molecular lines. Therefore, understanding how clouds impact observations is crucial to understanding observations. In Hot Jupiters, the cold night side are typically cloudy whereas the hot day sides are mostly cloud free. This uneven cloud coverage combined with their strong equatorial winds result in observations where half of the exoplanet is observed cloudy and the other half cloud free.
In this project, the student modeled the effect of asymmetric exoplanet atmospheres on transit observations. The model was used to produce observation simulation including error bars for state-of-the-art instrumentation.

On Earth, the greenhouse effect is well known and the leading cause of global warming. Sunlight passes through Earth's atmosphere mostly unhindered and heats our planet. Similarly, the Earth radiates heat into outer space but at longer wavelengths. Unfortunately, the same atmospheric gases that are transparent for sunlight are opaque for Earth's heat radiation (see figure 1). The radiation gets absorbed by the atmosphere and is partially re-emitted back to the ground thus trapping the heat and raising Earth's temperature. In addition to the gas, clouds are obscuring the atmosphere and influence the local and global temperature of planets. Even though the greenhouse effect is bad for us, it can be favourable for exoplanets. The increased temperature caused by greenhouse effects can help to keep an otherwise cold planet warm enough for liquid water to exist. This includes planets outside the habitable zone which is defined as the orbital distance from a star at which the net radiation results in temperatures between the freezing and evaporation point of water (without taking the planets atmosphere into account).
In this project, the goal is to develop a model to computationally study the greenhouse effect caused by exoplanet clouds and atmosphere using a 5 layer computational model. Looking at Venus with only an atmosphere (no clouds), a Greenhouse factor smaller than unity is calculated. This would mean a cooler surface on Venus. However, this cooling is not persent in Venus. This leads to the conclusion that the model is too simplified and needs to be expended for accurate predictions.

On Earth, the greenhouse effect is well known and the leading cause of global warming. Sunlight passes through Earth's atmosphere mostly unhindered and heats our planet. Similarly, the Earth radiates heat into outer space but at longer wavelengths. Unfortunately, the same atmospheric gases that are transparent for sunlight are opaque for Earth's heat radiation (see figure 1). The radiation gets absorbed by the atmosphere and is partially re-emitted back to the ground thus trapping the heat and raising Earth's temperature. Even though the greenhouse effect is bad for us, it can be favourable for exoplanets. The increased temperature caused by greenhouse effects can help to keep an otherwise cold planet warm enough for liquid water to exist. This includes planets outside the habitable zone which is defined as the orbital distance from a star at which the net radiation results in temperatures between the freezing and evaporation point of water (without taking the planets atmosphere into account). Therefore, to understand and quantify the greenhouse effect on exoplanets, it is crucial to understand which gases can influence the ground temperature of exoplanets.
The main goal of this project is to estimate the temperature of a planet given its atmospheric composition. Despite making multiple simplifications and assumptions, the model predicts equilibrium temperatures which resemble literature values of planetary temperatures without greenhouse effect. The estimated temperatures of the endoplanets with greenhouse effect tend to be lower than the currently available data for these temperatures. Especially for Venus, the estimated temperature is lower than current measurements suggest.

In the last decades over 4000 exoplanets have been discovered. Most of them by indirect measurements (like transits or radial velocity) but some were directly imaged. To observe exoplanets with high contrast imaging, state-of-the-art technology is required to overcome the two main challenges: high angular resolution and high contrast. One example of such an instrument is the Very Large Telescope (VLT) equipped with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE). But telescopes alone are not sufficient to find the very faint exoplanets and advanced image processing techniques have to be developed and constantly improved. The python package PynPoint contains such processing techniques to analyse observations of SPHERE. One of the core functionalities implemented into PynPoint is angular differential imaging (ADI) which helps to reduce the brightness of the host star and reveal faint companions. Recently, PynPoint was updated and now supports SPHERE/IFS data which allows to process spectral observations through spectral differential imaging (SDI). This additional information can help to improve current techniques and can be used to characterize exoplanets.
In this research angular differential imaging (ADI), spectral differential imaging (SDI) and the combinations of both methods were applied on 3 different systems using principal component analysis. This analysis gives the opporunity to subtract certain information of our data with the use of principal components. The results show that the signal to noise ratio is consistenly bigger with the combination of ADI and SDI than the methods itself. With the information of the position of the planet, properties of the orbit if the planet could me examined. These results match the values of literature, which indicates that the detection went well.

Optical and telescopic technology is coupled with software and computational coding to make the best images. Here, we have investigated how different techniques of manipulating data obtained from the SPHERE telescope in Chile can lead to better and stronger seeing of a distant planet going around its host star. The techniques used in this research are Angular Differential Imaging (ADI), Spectral Differential Imaging (SDI), Angular-Spectral Differential Imaging (ASDI), Spectral-Angular Differential Imaging (SADI), and Combined Differential Imaging (CODI). All of these can be coupled with Principal Component Analysis (PCA) which can help further simplify and reduce the large amount of data available.

Though the results are best seen graphically and require more than a few words to describe accurately, we can generalize or simplify the results by saying that using more complex data reduction tools (ASDI, SADI, and CODI) allows for better contrast between a host star and its observed exoplanet. This is further improved by the use of small, but not unary PCAs in the various reductions.

On Earth, the greenhouse effect is well known and the leading cause of global warming. Sunlight passes through Earth's atmosphere mostly unhindered and heats our planet. Similarly, the Earth radiates heat into outer space but at longer wavelengths. Unfortunately, the same atmospheric gases that are transparent for sunlight are opaque for Earth's heat radiation (see figure 1). The radiation gets absorbed by the atmosphere and is partially re-emitted back to the ground thus trapping the heat and raising Earth's temperature. Even though the greenhouse effect is bad for us, it can be favourable for exoplanets. The increased temperature caused by greenhouse effects can help to keep an otherwise cold planet warm enough for liquid water to exist. This includes planets outside the habitable zone which is defined as the orbital distance from a star at which the net radiation results in temperatures between the freezing and evaporation point of water (without taking the planets atmosphere into account). Therefore, to understand and quantify the greenhouse effect on exoplanets, it is crucial to understand which gases can influence the ground temperature of exoplanets.
An analysis of the sun’s luminosity, earth’s atmosphere, and earth’s thermal equilibrium is carried out to illuminate the nature of the atmospheric effects of greenhouse gases. This model can be extended to atmospheres with different input parameters, namely from other solar and extra-solar planets and their stellar hosts. In this research, a simplified approach to a dynamic system is taken, this means that the model accounts for single spherical stars, circular planetary orbits, a uniform, well-mixed, and homogeneous planetary atmosphere, and thermodynamic equilibrium in all parts of the system.

Machine learning algorithms are a powerful tool if used correctly. The first computational models using neural networks were developed in the 1940s. Since then, the field of machine learning has steadily grown and today’s algorithms are highly advanced but also incredibly complicated. Therefore, one has to be careful applying them because each algorithm has its pros and cons. In astrophysics, the power of machine learning is slowly being discovered and machine learning is more and more used for tasks which are otherwise difficult to solve. One such task is the calculation of cloud particle opacities. Even though the calculation is well studied, it takes a long time to get precise results. Currently, linear approximations and grid interpola- tions are used to overcome this problem, but as cloud opacity calculations are non-linear, their precision is limited. Fortunately, machine learning might be able to help. Neural networks, for example, have the ability to learn non-linear dependencies and thus can predict values of non-linear functions precisely and fast.
The potential of ML (machine learning) in accelerating Mie scattering codes is researched, for the particular application of calculating radiative feedback in exoplanet atmospherers. Mie scattering theory describes the interaction between electromagnetic plane waves and particles of micro- scopic size. This model plays a role in a larger scheme to understand atmospheric exoplanet data measured during transit.

Exomoon is a theater play organized by Pieter Steyart. The play imagines the distant futures when humankind expanded to other star systems. A new population of people who never knew earth will explor this worlds. On a moon within one of these systems, several explorer who departed from earth centuries ago are still frozen in cryogenic sleep. The people already living there decide to wake up the long asleep travelers. The guests of the exhibition take the role of these explorers and discover a new world.

My part during this play was a lecture about exoplanet climates at the very end of the play. In my talk, I told the audience about the strange and fascinating diversity of exoplanet climates. I told them about the winds, temperature and composition of hot Juptiers and terrestrial exoplanets. After going thorough the hole exhibition, the audience was eager to learn more more and I had some interesting conversation after the theater ended.

The BLOOM festival is an annual event in Copenhagen with a divers program all around nature and science. The attractions range from talks to concerts and are suitable for all ages. Happening in a central park in Copenhagen it is conveniently reachable. The beautiful weather helped to get many people interested in enjoying a nice day at the park and learn all about slightly different science.

Together with Pieter Steyart and Jesper Bruun, I was part of the experimental LARP (Life Action Roll Playing) called Exploring Exoplanets. In it, participants took on the role of a select group of people on board an inter-generational spaceship on the way to TRAPPISTENUM. They are to become the first human colony outside the Solar System. The participants than needed to decide which plant to built their first colony on, how to approach the planet, and how they wanted to govern the future society.

It was fascinating to see, how a divers group of people interacted with scientific data, how they approached the tasks, and get immersed in the story. Especially in the Q&A session afterwards, the questions I received about exoplanets were in much more detail than after conventional outreach talks. For me this experience showed once more that art can help to better communicate our work and foster scientific ideation.

Having your own personal webpage as a research has many advantages. First and foremoest it allowes people to find you and learn more about your research but they are also a great way to showcase your additional activities. In this tutorial, Till Käufer and I showed early career scientiets why they should have their own webpage, the dos and don'ts of webpage design and led a tutorial on how to create one. During this workshop, several people were able to create the first functioning draft of their webpage. Do you want to create your own personal webpage? Feel free to contact me or look through our slides!

Teach the Teachers is a series of talks for teachers given by exoplanet scientiests. The goal is to give the teachers a glimbs into current astrophysics reasearch and to show the relevence of this topics for their class room. The first lesson is on cloud formation. Students can gather first-hand experience by creating their own clouds using simple household items such as a jar, soap, ice, hot water and hairspray. Thanks to the detailed descriptions developed by Oriel, the students can easily connect their lab work to real cloud formation on our and other planets. The second lesson she designed is focused around lighting. Similar to the first one, students learn difficult physical process by experimenting with simple household items.

In the first presentation, Oriel Marshall, Helena Lecoq, Aaron Schneider and I presented a general overview of astrophysics to a group of teachers. We also gave a more detailed view of our individual research topics to show them what contemporary exoplanet science looks like. It was amazing to see the fascination of teachers for space and exoplanets. Their questions went well beyond the topics we covered in the presentation and showed their vested interest.

After a year of hard work, Oriel Marshall has created teaching materials built on the research topics of the CHAMELEON Network. One of the main strengths of the CHAMELEON Network is the combination of not only physics research but extending to arts and education. I had the pleasure to help Oriel develop the cloud formation lessons and present it to teachers who can then test it in a real classroom setting. With this presentation, Oriel introduced the teachers to the lessons, and I presented the current state of exoplanet cloud formation. It was fascinating to see once more that teachers are as curious and filled with questions as their students.

Oriel Marshall is presenting her work to a group of teachers to motivate them to use her newly developed cloud formation lessons. To show the roots of her lessons in current exoplanetary research, Nanna Bach-Møller and I present our current work. Nanna is presented recent aerosol experiments which she conducted in the laboratory of the University of Copenhagen. I presented the basics of 3D exoplanet climate modelling and why it is important to know about their clouds.
Seeing the motivation of teachers to learn about new scientific concepts and their eager to add it to an already pack-full curriculum is inspiring. Conducting research on a PhD level somtimes feels disconnected from the real world, but through the work of Oriel and the engagement of teachers we are able to bring our research to students and the broader public.

Here on Earth, weather is one of the most important small talk topics, but what would we talk about if we were on an exoplanet? Thanks to state-of-the-art instrumentation and advanced modelling, we are beginning to understand the fascinating diversity of weather on planets outside of our own solar system.
Exoplanet surveys like Kepler have discovered thousands of exoplanets, meaning, we are now aware of the large diversity of exoplanets that exist in our galaxy. The next step is now to characterise these exoplanets. With current state-of-the-art technology, we are already starting to gain insights into their atmospheres, and with upcoming instruments like the James Webb Space Telescope (JWST) we hope to deepen our understanding of these alien worlds.
Some of the most fascinating objects discovered so far are Hot Jupiters: planets the size of Jupiter but with orbital periods of just days. These giant gas planets are tidally locked, which results in permanent day and permanent night sides. The temperature, winds and clouds on these planets are nothing like what we know from planets within our solar system and understanding them is the first step to understanding the diverse atmospheres of exoplanets.

This winter school organised by the Meta futurism lab took its participants far away from the Earth. The participants were thrown onto another planet where they had to find imaginative ways to live, survive and prosper. One of the aliens they imagined can be seen in the picture. During their exploration of this new world, they were confronted with challenges which they had to overcome. In the end, the participants used their experience to create a short and interactive show.
Oriel Marshall and I were the scientific experts for this event. Our task was to answer all exoplanet and science related questions from the participants. We also asked critical questions about their ideas and tried to motivate them to further develop their solutions. All participants were highly motivated and involved in the project which made the whole day a fascinating and motivating experience.

The "Dag van de Wetenschap" aims to bring science closer to the general public. For this event, I presented a general introduction into astrophysics and exoplanet science. I covered the formation, detection and types of exoplanets. I also gave a quick overview of what we currently know about life on other planets. The full presentation can be found on YouTube.