Stellar Flybys Interrupting Planet-Planet Scattering Generates Oort Planets

Abstract

Wide-orbit exoplanets are starting to be detected, and planetary formation models are under development to understand their properties. We propose a population of "Oort" planets around other stars, forming by a mechanism analogous to how the Solar System's Oort cloud of comets was populated. Gravitational scattering among planets is inferred from the eccentricity distribution of gas-giant exoplanets measured by the Doppler technique. This scattering is thought to commence while the protoplanetary disk is dissipating, $10^6-10^7$ yr after formation of the star, or perhaps soon thereafter, when the majority of stars are expected to be part of a natal cluster. Previous calculations of planet-planet scattering around isolated stars have one or more planets spending $10^4-10^7$ yr at distances >100 AU before ultimately being ejected. During that time, a close flyby of another star in the cluster may dynamically lift the periastron of the planet, ending further scattering with the inner planets. We present numerical simulations demonstrating this mechanism as well as an analysis of the efficiency. We estimate an occurrence of planets between 100 and 5000 AU by this mechanism to be <1% for gas giants and up to a few percent for Neptunes and super-Earths.

arXiv comment15 pages, 11 figures, submitted to AJ

References in corpus (49)

• Embedded Clusters in Molecular Clouds
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• Dynamical Outcomes of Planet-Planet Scattering
• IAS15: A fast, adaptive, high-order integrator for gravitational dynamics, accurate to machine precision over a billion orbits
• Protoplanetary Disk Structures in Ophiuchus
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Dynamical Origin of Extrasolar Planet Eccentricity Distribution
• Unbound or Distant Planetary Mass Population Detected by Gravitational Microlensing
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• The Birth Environment of the Solar System
• Can giant planets form by direct gravitational instability?
• Evidence for a Distant Giant Planet in the Solar System
• Imaging Extrasolar Giant Planets
• No large population of unbound or wide-orbit Jupiter-mass planets
• Dynamical Evolution of the Early Solar System
• Formation of the Widest Binaries from Dynamical Unfolding of Triple Systems
• Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12
• Rapid inward migration of planets formed by gravitational instability
• Migration of extrasolar planets to large orbital radii
• The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
• The Effect of Encounters on the Eccentricity of Binaries in Clusters
• Formation, Survival, and Detectability of Planets Beyond 100 AU
• Clouds in the Coldest Brown Dwarfs: FIRE Spectroscopy of Ross 458C
• The Effects of a Stellar Encounter on a Planetesimal Disk
• On the origin of planets at very wide orbits from the re-capture of free floating planets
• The dynamical evolution of multi-planet systems in open clusters
• Instability-Driven Dynamical Evolution Model of a Primordially 5 Planet Outer Solar System
• A Neptune-mass Free-floating Planet Candidate Discovered by Microlensing Surveys
• Dynamical Interactions of Planetary Systems in Dense Stellar Environments
• Hydrogen delivery onto white dwarfs from remnant exo-Oort cloud comets
• Properties of the Distant Kuiper Belt: Results from the Palomar Distant Solar System Survey
• Constraints on the location of a possible 9th planet derived from the Cassini data
• Survivability of planetary systems in young and dense star clusters
• Not all stars form in clusters - measuring the kinematics of OB associations with $Gaia$
• Evaporation and Accretion of Extrasolar Comets Following White Dwarf Kicks
• Dynamical Evolution of Young Embedded Clusters: A Parameter Space Survey
• Constraints on the acceleration of the solar system from high-precision timing
• The curiously warped mean plane of the Kuiper belt
• Interaction Cross Sections and Survival Rates for Proposed Solar System Member Planet Nine
• The dynamical fate of planetary systems in young star clusters
• Astrometric Microlensing Constraints on a Massive Body in the Outer Solar System with Gaia
• Searching for Scatterers: High-Contrast Imaging of Young Stars Hosting Wide-Separation Planetary-Mass Companions
• Producing Distant Planets by Mutual Scattering of Planetary Embryos
• Two Thresholds for Globular Cluster Formation and their Dominance of Star Formation in the Early-Universe
• A serendipitous all sky survey for bright objects in the outer solar system
• High Contrast Imaging with Spitzer : Constraining the Frequency of Giant Planets out to 1000 AU separations
• A Near-coplanar Stellar Flyby of the Planet Host Star HD 106906
• WEIRD: Wide-orbit Exoplanet search with InfraRed Direct imaging
• Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt

Cited by in corpus (7)

• Population-Level Eccentricity Distributions of Imaged Exoplanets and Brown Dwarf Companions: Dynamical Evidence for Distinct Formation Channels
• Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments are Common
• Exciting spiral arms in protoplanetary discs from flybys
• Tilting Uranus via Secular Spin-Orbit Resonance with Planet 9
• Peculiar orbits and asymmetries in extreme trans-Neptunian space
• Very-wide-orbit planets from dynamical instabilities during the stellar birth cluster phase
• Exoplanet Occurrence Rates from Microlensing Surveys