Is our Sun a Singleton?

TL;DR

This paper investigates how stellar encounters in clusters influence the formation and evolution of planetary systems, proposing that our Sun may be a singleton that avoided such interactions, thus preserving a solar-like planetary system.

Contribution

It introduces the concept of a singleton star and analyzes how stellar encounters impact planetary system architectures, highlighting the importance of a star's formation environment.

Findings

Close encounters can alter planetary orbits, making them more eccentric.

Singleton stars are likely to host planetary systems similar to our solar system.

Many observed exoplanet systems may result from stars that experienced stellar interactions.

Abstract

Most stars are formed in a cluster or association, where the number density of stars can be high. This means that a large fraction of initially-single stars will undergo close encounters with other stars and/or exchange into binaries. We describe how such close encounters and exchange encounters can affect the properties of a planetary system around a single star. We define a singleton as a single star which has 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, often leaving planets on tighter and more eccentric orbits. Thus planetary systems which initially resembled our own solar system may later more closely resemble some of the observed exoplanet systems.