The Solar System as an Exoplanetary System

TL;DR

This study statistically compares the Solar System to exoplanetary systems, finding it broadly typical except for the absence of super-Earths and inner planets, suggesting our Solar System is not extremely rare.

Contribution

The paper introduces a mathematical transformation for meaningful comparison between the Solar System and exoplanets, revealing its typicality and specific differences.

Findings

Solar System's giant planets are typical in mass and density.

Orbital location of Jupiter is an outlier likely due to selection bias.

Lack of super-Earths and inner planets makes Solar System somewhat unique.

Abstract

With the availability of considerably more data, we revisit the question of how special our Solar System is, compared to observed exoplanetary systems. To this goal, we employ a mathematical transformation that allows for a meaningful, statistical comparison. We find that the masses and densities of the giant planets in our Solar System are very typical, as is the age of the Solar System. While the orbital location of Jupiter is somewhat of an outlier, this is most likely due to strong selection effects towards short-period planets. The eccentricities of the planets in our Solar System are relatively small compared to those in observed exosolar systems, but still consistent with the expectations for an 8-planet system (and could, in addition, reflect a selection bias towards high-eccentricity planets). The two characteristics of the Solar System that we find to be most special are the lack of super-Earths with orbital periods of days to months and the general lack of planets inside of the orbital radius of Mercury. Overall, we conclude that in terms of its broad characteristics our Solar System is not expected to be extremely rare, allowing for a level of optimism in the search for extrasolar life.