Here, I present an overview of my current and past research projects. I mainly use hydrodynamical codes to investigate problems in planet formation. However, I'm also interested in planetary dynamics, N-body methods and lots of other topics.
Surface density of a simulation with three embedded planets. The frame is corotating with the outermost Neptune-mass planet. We can see spiral arms caused by all three planets interacting with it. The resulting time-varying torque on the planet (blue) is shown in the bottom panel, together with a moving time-average (orange).
When planets are still embedded in their parent protoplanetary disk of dust and gas, gravitational interaction allows them to change their orbits in a process which is called orbital migration. It comes in different flavours and can be directed either inward or outward, depending on planet masses and the Physics that are included in hydrodynamical simulations to model it. The existence of orbital resonances in exoplanet systems is considered as strong evidence for the significance of this mechanism in shaping their architecture. Currently, I am looking at how differential migration of multiple embedded planets can lead to the formation of resonant chains by employing hydrodynamical simulations. While N-body simulations are much faster, they use analytical prescriptions for the torques that allow the planets to move. Prominent examples for such systems are GJ 876, which hosts four discovered planets, three of which are in a 4:2:1 Laplace resonance. The system around TRAPPIST-1, has made the news for hosting mutliple earth-size planets in resonance. This work is done in collaboration with Willy Kley and Rolf Kuiper.
N.P. Cimerman, W. Kley, & R. Kuiper (2018)
Formation of a planetary Laplace resonance through migration in an eccentric disk - The case of GJ876
Astronomy and Astrophysics, in press (ADS, arXiv)
Time evolution of the radial entropy profile in the atmosphere. We compare a 1D isolated (solid) to a 3D open, hydrodynamic (dashed) atmosphere.
Together with Rolf Kuiper and Chris Ormel, I investigated the role of planet-disk interactions for super-Earth planets in the evolution of their atmospheres. Previous studies suggested that a continuous exchange of gas between the atmosphere and a gas-rich protoplanetary disk could save super-Earths from accumulating envelopes of cricitical mass, which would lead to runaway gas accretion, transforming them into gas giants. To directly model close in (0.1 au), embedded super-Earths, we employed three-dimensional radiation hydrodynamics, using a modified version of the PLUTO code. The animation on the left shows a radial profile of the gas entropy in the proto-atmosphere, comparing open, 3D (dashed) to spherically symmetric, 1D (solid) models. Due to radiative cooling, the gas loses entropy and the atmosphere contracts. While the isolated atmosphere continues to cool, the 3D model maintains higher entropy due to the advective recycling of gas and shows some convergence to a steady state. This proves that resolving the interaction of super-Earths with their nascent disk can and does affect the thermal evolution of their atmospheres. This provides an explanation for the origin of the most commonly discovered class of exoplanets.
N.P. Cimerman, R. Kuiper, & C.W. Ormel (2017)
Hydrodynamics of embedded planets' first atmospheres - III. The role of radiation transport for super-Earth planets
Monthly Notices of the Royal Astronomical Society, Volume 471, Issue 4, p.4662-4676 (ADS, arXiv, MNRAS)