Exoplanets -- dynamical Habitability -- Solar System -- Chaos
Exoplanets:

is the principal topic of my astrophysical research. The numerous extra-solar planets detected so far learned us that planetary systems might be quite different compared to our solar system. Therefore, studies of these systems either in general or for individual ones became a special focus of astrophysical research, covering e.g.

(i) observations, (ii) orbit determination, (iii) formation processes (either hydrodynamical studies or n-body simulations), (iv) stability studies as well as (v) the interdisciplinary research of habitability .

I mainly work on the topics marked in orange; where different dynamical configurations have to be considered: (1) single-star single-planet systems -- (2) single-star multi-planet systems -- (3) planets in double star systems.

Habitability (dynamical):

The detection and investigation of Earth-like exo-planets may have great importance for further improvements of formation theories of our Solar system, where both rocky Earth-like and gaseous Jupiter-like planets had been formed. Another major question which has a special interest -- not only for the scientific community -- is whether life may have evolved in other planetary systems. The region of a planetary system, where life might exist is called habitable zone (HZ). The basic requirement for the HZ is according to the famous scientific work by Kasting and co-worker that liquid water is stable on the surface of an EarthBB-like planet.

Since the evolution of a biosphere is a process over a very long time, long-term stability of the planetary system is an important condition for the habitability which underlines the necessity of stability studies.

Solar System Dynamics:

Our solar system serves as reference system for other planetary systems. We expect that there are planetary systems with similar characteristics like ours. Probably they are farther away and have not been discovered yet. The recent detection by Gaudi and co-workers (known as OGLE 06-109L system) using microlensing is maybe a first indication for this. Studies using the parameters of the solar system and varying them will certainly provide important results for future discoveries in the extra-solar planetary research.

Planets in Double Star Systems:

The study of double star systems is important due to the fact that more than 60 % of the stars in the solar neighborhood build such systems -- which are interesting systems from the dynamical point of view. As the stable planetary motion is restricted to certain regions of the phase space of a system due to the gravitational interactions between the celestial bodies, especially if the perturbing star is quite close. Moreover, different types of motion have to be considered, depending on the distance between the two stars: We can observe planets moving either around one stellar component or in a distant orbit around both. Theoretically another configuration could be possible, where the planet moves in the same orbit like the smaller star (one has to note that the mass-ratio of the two stars has to be < 1/26 to have a stable configuration) but 60[deg] ahead or behind this stellar component so that they are locked in 1:1 mean motion resonance, which allows a stable planetary motion.

Since we expect an increasing number of planetary detections in binary systems the study of such systems provides an important contribution for future observations.

Chaos Indicators:

LLCNs: Local Lyapunov Characteristic Numbers -- Thesis in collaboration with Dr. Claude Froeschle, Observatory of Nice, France

FLI: Fast Lyapunov Indicator -- Fast numerical methods based on the Lyapunov characteristic exponent to determine the dynamical state of the orbital motion in a planetary system.