Turning solar systems into extrasolar planetary systems in stellar clusters

Abstract

Abstract. Many stars are formed in some form of cluster or association. These environments can have a much higher number density of stars than the field of the galaxy. Such crowded places are hostile environments: a large fraction of initially single stars will undergo close encounters with other stars or exchange into binaries. We describe how such close encounters and exchange encounters will affect the properties of a planetary system around a single star. We define singletons as single stars which have never suffered close encounters with other stars or spent time within a binary system. It may be that planetary systems similar to our own solar system can only survive around singletons. Close encounters or the presence of a stellar companion will perturb the planetary system, leading to strong planet-planet interactions, often leaving planets on tighter and more eccentric orbits. Thus, planetary systems which initially resembled our own solar system may later more closely resemble the observed extrasolar planetary systems.

A likely flyby of binary protostar Z CMa caught in action

“…Flyby occurrence rate estimate. In young clusters with a stellar mass density ρ cluster of a few 100s−1000 M pc −3 , one can estimate the average time required for a particular star to experience a flyby by another star passing within a pericenter distance r peri as 81,82 :…”