Long period planets from dynamical relaxation

TL;DR

This paper investigates whether dynamical relaxation and planet scattering can explain the existence of massive, long-period planets observed around stars, using N-body simulations to explore their formation and distribution.

Contribution

It demonstrates through simulations that dynamical relaxation can produce long-period giant planets, offering a new explanation for their observed populations.

Findings

Dynamical relaxation can scatter planets to large orbits (~1000 AU).

Simulations match observed long-period planet distributions.

Direct imaging and microlensing are complementary in studying this process.

Abstract

Recent imaging campaigns indicate the likely existence of massive planets (~ 1-10 MJ) on ~1000 year orbits about a few percent of stars. Such objects are not easily explained in most current planet formation models. In this Letter we use ensembles of 100 N-body simulations to evaluate the potential for planet scattering during relaxation of dynamically active systems to explain the population of giant planets with projected separations up to a few 100 AU. We find that such a mechanism could indeed be at play, and that statistical samples of long period planets could place interesting constraints on early stage planet formation scenarios. Results from direct imaging and microlensing surveys are complementary probes of this dynamical relaxation process.