Oort cloud (exo)planets

Abstract

Dynamical instabilities among giant planets are thought to be nearly ubiquitous, and culminate in the ejection of one or more planets into interstellar space. Here we perform N-body simulations of dynamical instabilities while accounting for torques from the galactic tidal field. We find that a fraction of planets that would otherwise have been ejected are instead trapped on very wide orbits analogous to those of Oort cloud comets. The fraction of ejected planets that are trapped ranges from 1-10%, depending on the initial planetary mass distribution. The local galactic density has a modest effect on the trapping efficiency and the orbital radii of trapped planets. The majority of Oort cloud planets survive for Gyr timescales. Taking into account the demographics of exoplanets, we estimate that one in every 200-3000 stars could host an Oort cloud planet. This value is likely an overestimate, as we do not account for instabilities that take place at early enough times to be affected by their host stars' birth cluster, or planet stripping from passing stars. If the Solar System's dynamical instability happened after birth cluster dissolution, there is a ~7% chance that an ice giant was captured in the Sun's Oort cloud.

arXiv commentMNRAS Letters, in press. Blog post about paper at https://planetplanet.net/2023/06/21/oort-cloud-exoplanets/

References in corpus (33)

• Dynamical Outcomes of Planet-Planet Scattering
• Catalog of Nearby Exoplanets
• Dynamical Origin of Extrasolar Planet Eccentricity Distribution
• The Birth Environment of the Solar System
• Statistical Study of the Early Solar System's Instability with 4, 5 and 6 Giant Planets
• No large population of unbound or wide-orbit Jupiter-mass planets
• Dynamics of the giant planets of the solar system in the gaseous proto-planetary disk and relationship to the current orbital architecture
• A New Planet Around an M Dwarf: Revealing a Correlation Between Exoplanets and Stellar Mass
• Dynamical Evolution of the Early Solar System
• The Exoplanet Mass-Ratio Function from the MOA-II Survey: Discovery of a Break and Likely Peak at a Neptune Mass
• Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate
• Giant planets orbiting metal-rich stars show signatures of planet-planet interactions
• Oort Cloud and Scattered Disc formation during a late dynamical instability in the Solar System
• Planetary System Disruption by Galactic Perturbations to Wide Binary Stars
• Debris disks as signposts of terrestrial planet formation
• Planet-planet scattering in planetesimal disks II: Predictions for outer extrasolar planetary systems
• Migration and Dynamical Relaxation in Crowded Systems of Giant Planets
• Debris disks as signposts of terrestrial planet formation. II Dependence of exoplanet architectures on giant planet and disk properties
• The Formation of the Oort Cloud in Open Cluster Environments
• Planet-planet scattering leads to tightly packed planetary systems
• Mean motion resonances from planet-planet scattering
• A rich population of free-floating planets in the Upper Scorpius young stellar association
• Spitzer Evidence for a Late Heavy Bombardment and the Formation of Urelites in η Corvi at ~1 Gyr
• Instability-Driven Dynamical Evolution Model of a Primordially 5 Planet Outer Solar System
• Synthesizing Exoplanet Demographics: A Single Population of Long-Period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys
• Evolution over time of the Milky Way's disc shape
• Outward migration of Jupiter and Saturn in 3:2 or 2:1 resonance in radiative disks: implications for the Grand Tack and Nice models
• How to design a planetary system for different scattering outcomes: giant impact sweet spot, maximising exocomets, scattered disks
• The Demographics of Rocky Free-Floating Planets and their Detectability by WFIRST
• Born eccentric: constraints on Jupiter and Saturn's pre-instability orbits
• Oort cloud Ecology II: Extra-solar Oort clouds and the origin of asteroidal interlopers
• The Influence of Outer Solar System Architecture on the Structure and Evolution of the Oort Cloud
• Secular Behavior of Exoplanets: Self-Consistency and Comparisons with the Planet-Planet Scattering Hypothesis

Cited by in corpus (1)

• Very-wide-orbit planets from dynamical instabilities during the stellar birth cluster phase