Long-period exoplanets from dynamical relaxation

Abstract

Recent imaging campaigns indicate the likely existence of massive planets (1-10MJ ) 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 100AU. 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. © 2009. The American Astronomical Society. All rights reserved..