Orbital structure of planetary systems formed by giant impacts: stellar mass dependence

TL;DR

This study uses N-body simulations to explore how stellar mass influences the formation and orbital architecture of planetary systems resulting from giant impacts, revealing that lower-mass stars tend to produce fewer, more massive, and more dynamically excited planets.

Contribution

It provides the first systematic analysis of stellar mass dependence on planetary system architecture formed by giant impacts, extending understanding to low-mass stars.

Findings

Planet mass increases as stellar mass decreases.

Number of planets decreases with lower stellar mass.

Orbital eccentricity and inclination increase as stellar mass decreases.

Abstract

Recent exoplanet surveys revealed that for solar-type stars, close-in Super-Earths are ubiquitous and many of them are in multi-planet systems. These systems are more compact than the Solar System's terrestrial planets. However, there have been few theoretical studies on the formation of such planets around low-mass stars. In the standard model, the final stage of terrestrial planet formation is the giant impact stage, where protoplanets gravitationally scatter and collide with each other and then evolve into a stable planetary system. We investigate the effect of the stellar mass on the architecture of planetary systems formed by giant impacts. We perform {\it N}-body simulations around stars with masses of 0.1--2 times the solar mass. Using the isolation mass of protoplanets, we distribute the initial protoplanets in 0.05--0.15 au from the central star and follow the evolution for 200 million orbital periods of the innermost protoplanet. We find that for a given protoplanet system, the mass of planets increases as the stellar mass decreases, while the number of planets decreases. The eccentricity and inclination of orbits and the orbital separation of adjacent planets increase with decreasing the stellar mass. This is because as the stellar mass decreases, the relative strength of planetary scattering becomes more effective. We also discuss the properties of planets formed in the habitable zone using the minimum-mass extrasolar nebula model.