Solar system formation
There are a number of indications that the Solar system formed in a massive cluster. The cut-off radius of the planetary system at 30 AU and the high eccentricity of the trans neptunian objects indicate that the solar system likely had an encounter with another star during its formation phase. We investigate how these solar system properties constrain the actual fly-by parameters and the properties of its birth cluster.
The discovery of 1I/‘Oumuamua confirmed that planetesimals must exist in great numbers in interstellar space. Originally generated during planet formation, they are scattered from their original systems and subsequently drift through interstellar space. We investigate what consequences the existence of such objects might have.
Young cluster development
Most stars do not form in isolation but as part of a stellar group consisting of a few dozen to several million stars with stellar densities ranging from 0.01 to several 100 M⊙ pc-3. The majority of these clusters dissolve within 20 Myr. The general assumption is that clusters are born more or less over this entire density range. Our research shows that clustered star formation works under surprisingly tight constraints with respect to cluster size and density. The observed multitude of cluster densities simply results from snapshots of two sequences evolving in time along pre-defined tracks in the density-radius plane.
Discs in young clusters
Young stars are initially surrounded by discs consisting of dust and gas. It is those discs that planetary systems can develop from, if the conditions are favourable. In young dense clusters the star-disc systems can interact with each other resulting in changes in the disc. Investigating how the cluster environment changes the disc properties is one of the central themes of our work.
Binaries in clusters
Binary stars are very common. Especially massive stars are mainly not single stars but binaries or even higher order multiples. Young dense clusters can have very high densities so that their members may interact strongly. These interactions can lead to the destruction of binaries but also to their formation. in addition, can the interaction of just formed binaries with the surrounding gas that leads to a decrease in the orbit and in extreme cases even to mergers.
The common denominator are N-body methods. We develop highly efficient hierarchical tree codes. In addition we apply and develop diagnostics for SPH simulations, and various Body codes with higher order integrators to study the dynamics of these objects.
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