Institut für Planetenforschung Berlin-Adlershof

The discovery of Extrasolar Planetary Systems (EPS) and their diverse structure has raised questions about the existing formation scenarios for the Solar System and their applicability on other stellar systems. Basic orbital properties (semi-major axis (a), eccentricity (e) and minimum planetary mass (m•sin i)), are only known for a limited number of EPS, but some are quite different from the Solar System, with Jupiter sized planets in close and eccentric orbits around the central star. Even if the discovery of such systems is mainly a consequence of observational selection effects, their nature indicates a different evolution history compared to the Solar System.

The time evolution of extrasolar planetary orbits can be studied by monitoring the time variation in orbital Kepler elements using n-body integration schemes. Basically, n-body integrators solve the equation of motion by numerically propagating the system, given an initial start configuration. Thus, following a given EPS over a substantial part of its lifetime, one obtains longterm variations in the orbital elements and insight into the complex nature of planetary system evolutionary mechanisms.

Related publications

Dynamical simulations of planetary systems as mission support (A. Erikson, H. Rauer)

Forthcoming space missions dedicated to the search for exoplanets via transits (e.g. COROT, Eddington) are expected to significantly increase the number of known exoplanetary systems. The dynamical evolution of a newly discovered system can be studied by numerical integrations of the equations of motions. By performing such integrations one can for each planetary system characterize its long term stability, improve observed orbital parameters and make predictions for follow-up observations. A software package (Xint) to perform the above tasks has been implemented and its application to the COROT and Eddington mission scenarios investigated.

Planetary Obliquity Evolution in the 47 UMa Habitable Zone (A. Erikson)

The obliquity evolutions of the terrestrial planets in the Solar System have a high probability of encountering chaotic regimes, thereby initiating large scale variations with profound implications for the long term atmosphere and surface conditions of the planets. The recent discovery of an extra solar planetary system (47 UMa), that could potentially harbor small terrestrial planets, has raised questions about the conditions for habitability in such a system. In that context the effects of the obliquity evolution might be of significance and has been numerically simulated for hypothetical small planets located in the habitable zone of 47 UMa. First results indicate that large but regular variations (~10º- 40º) on relative short time-scales (104 - 105 yr) could be present for such an object. The study was performed in collaboration with E. Skoglöv (Univ. Uppsala).
 

The spin axis evolution of a hypothetical Earth like planet located in the habitable zone of the 47 UMa system. The parameter X corresponds to the sinus of the spin axis latitude. The amplitude of the variation is around 20°.

Resonance phenomena in extrasolar planetary system (T.C. Hinse, A. Erikson, H. Rauer)

The nature and stability of mean motion resonances in extrasolar planetary systems have been studied by numerical integrations. Considering both first and second order resonances for a wide planetary mass range, the orbital parameter space around the resonances was searched for stable configurations. Such a mapping of the dynamical structure around the most common mean motion resonances could be used to further constrain the orbits and masses of newly discovered systems. The study is a part of the master thesis of T.C. Hinse (Univ. Copenhagen) who stayed for 6 months at DLR-PF on an Erasmus stipendium.

Dynamical Star-Planet Interaction (H. Rauer)

The currently found planets show a lack of close-in massive planets. It was investigated whether this phenomenon is caused by tidal interaction of the planet with its central star. It has been found that massive planet can spiral into the central star on time scale shorter than the stellar life time. Therefore, this mechanism may provide an explanation for the observed statistics of planets.

Group of Cometary Atmospheres and Extra-Solar Planets

Section Physics of Small Bodies and Extra-solar Planets