Consolidating and Crushing Exoplanets: Did it happen here?

TL;DR

This paper suggests that tightly-packed inner planet systems (STIPs) are initially common around stars and often undergo collisional consolidation or destruction over billions of years, with our Solar System's history possibly involving similar processes.

Contribution

It introduces a model where STIPs form universally and evolve through long-term metastability leading to system-wide collisions or destruction, explaining the rarity of such systems.

Findings

STIPs initially form around most FGK stars.

Long-term metastability leads to system collapse over Gyr timescales.

Our Solar System may have experienced similar collisional evolution.

Abstract

The Kepler mission results indicate that systems of tightly-packed inner planets (STIPs) are present around of order 5% of FGK field stars (whose median age is ~5 Gyr). We propose that STIPs initially surrounded nearly all such stars and those observed are the final survivors of a process in which long-term metastability eventually ceases and the systems proceed to collisional consolidation or destruction, losing roughly equal fractions of systems every decade in time. In this context, we also propose that our Solar System initially contained additional large planets interior to the current orbit of Venus, which survived in a metastable dynamical configuration for 1-10% of the Solar System's age. Long-term gravitational perturbations caused the system to orbit cross, leading to a cataclysmic event which left Mercury as the sole surviving relic.