I am an astrophysicist working in the field of planet formation and evolution, both from a theoretical perspective and by observing exoplanet systems with state-of-the-art telescopes.
My research revolves around planet population synthesis and exoplanet demographics.
State-of-the-art planet formation models are more and more capable of accounting for the full spectrum of known planet types, but this comes at the cost of increasing model complexity. This calls into question whether established links between the initial conditions of the simulations and the calculated planetary observables are preserved. In our recently accepted paper, we take a data-driven approach to investigate such relations in a global model of planet formation and evolution. We first used a Gaussian Mixture Model to perform a cluster analysis on typical exoplanet observables such as planet radius, mass, and orbital distance. Interestingly, the algorithm identified roughly the same planet species as the ones defined by exoplanet observations (without knowing anything about the physical model or planet demographics!). Then, we trained a Random Forest Classifier to predict which planet type forms, given certain properties of the originating protoplanetary disk. This way, we could not only find the most predictive features of the disks, but also pinpoint the influence of gravitational interactions in multi-planet systems to specific planet types.
In this paper, we tested what planet formation has to say about a peculiar trend that has been found in exoplanet demographics: around solar-type stars, inner super-Earths and outer giant planets tend to occur together.
This challenges some established planet formation theories that predicted an anti-correlation of these planet types.
Our synthetic population of 1000 multi-planet systems supports the observed trend, but with important caveats.
When we associate our initial conditions with the composition of the resulting planets, we see a quite interesting link: Depending on the initial solid mass, we either get isolated, icy super-Earths or rocky ones that have a cold Jupiter companion. This gives rise to the testable hypothesis that high-density inner super-Earths are proxies for cold Jupiters in the same system. A confirmation of this prediction would constrain central open questions in contemporary planet formation theory, ranging from efficiency of pebble accretion to planet migration behavior.
The orbital parameters of warm Jupiters serve as a record of their formation history, providing constraints on formation scenarios for giant planets on close and intermediate orbits. In my study with the WINE (Warm gIaNts with tEss) collaboration, we report the discovery of a new exoplanet that we detected in full frame images of the TESS space telescope and followed up with ground-based photometry (CHAT and LCOGT) and radial velocity measurements (FEROS). We precisely constrained its mass to Mp= 1.94 +/- 00.1 Mj, and its radius to Rp = 1.24 +/- 0.15 Rj. It orbits a G-type star, similar to the Sun (Ms = 1.03 +/- 0.06 Msun, V = 12.1 mag), on one of the most eccentric orbits of all known warm giants. In fact, with a period of 15.17 d and e ≈ 0.58 its orbital parameters resemble those of the TESS spacecraft itself. This extreme dynamical state points to a past interaction with an additional, undetected massive companion. A tidal evolution analysis showed a large tidal dissipation timescale, suggesting that the planet is not a progenitor for a hot Jupiter caught during its high-eccentricity migration. This planet further represents an attractive opportunity to study the energy deposition and redistribution in the atmosphere of a warm Jupiter with high eccentricity.
Planet Population Synthesis is a holistic approach to study the conditions necessary for planet formation and evolution. It compares the properties of observed exoplanets, e.g. mass and orbital radius, to the ones obtained from planet formation simulations. This technique is particularly promising if one has access to an observational data set with a well-known detection bias that can be taken into account when comparing observations with theory.
We have adapted our formation model to low-mass stars in order to compare it to surveys like CARMENES, which searches for Earth-mass planets around nearby M-dwarf stars. Such comparisons will improve our understanding of different planet formation channels around stars of different masses.
The ExoEarth Discovery and Exploration Network (EDEN) transit survey is a large-scale search for transiting habitable zone Earth-sized planets around nearby stars. In contrast to most ongoing and past surveys, the EDEN team utilizes large research telescopes (0.8 m–2.4 m), which allows for efficient probing of the habitable zones of late M-dwarf stars.
I led a team of 14 PhD students and post-docs that observes with EDEN's workhorse, the Calar Alto 1.2 m telescope. As of 2021, we contributed more than 200 full nights of observations. Being interested in planet demographics, I am also involved in EDEN's target selection and survey statistics.
My trajectory in science
For my Master's project, I investigated irregular transit signatures in photometry of the Kepler space telescope.