Considering contact forces during the formation of planetesimals by gravitational collapse: mutual orbits, spin states, and shapes
arXiv:2507.16739 · doi:10.3847/1538-4357/ade142
Abstract
In this work, we apply a soft-sphere discrete element method (SSDEM) within the PKDGRAV N-body integrator to investigate the formation of planetesimal systems through the gravitational collapse of clouds of super-particles. Previously published numerical models have demonstrated that the gravitational collapse of pebble clouds is an efficient pathway to produce binary planetesimal systems. However, such investigations were limited by their use of a perfect-merger and inflated-radii super-particle approach, which inhibits any analysis of planetesimal shapes and spin states, precludes the formation of the tightest binary orbits, and produces significantly under-dense planetesimals. The SSDEM enables super-particles to rest upon each other through mutual surface penetration and by simulating contact physics. Super-particles do not need to be inflated and collisions are not treated as perfect mergers; we can thus track the evolution of planetesimal shapes, spins, and tight binary orbits. We demonstrate that the SSDEM is an excellent method to model the collapse process, and is capable of producing many binary planetesimal systems from a single cloud. Our results confirm the findings of previously published perfect-merging models while also producing novel results about planetesimal spin and shape properties. Newly-formed planetesimals exhibit 10-hr rotation periods on average and can be characterized by a wide variety of shapes (spherical, oblate, top-shaped, flattened, egg-shaped, or prolate), with the most-massive planetesimals primarily forming as spheres and oblate-spheroids.
Accepted for publication in ApJ. 34 pages, 17 figures, 5 tables
References in corpus (22)
- Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
- Close-in planetesimal formation by pile-up of drifting pebbles
- Evidence for Two Populations of Classical Transneptunian Objects: The Strong Inclination Dependence of Classical Binaries
- The Correlated Colors of Transneptunian Binaries
- Numerical predictions of surface effects during the 2029 close approach of asteroid 99942 Apophis
- Color, Composition, and Thermal Environment of Kuiper Belt Object (486958) Arrokoth
- The Brazil-nut effect and its application to asteroids
- Binary Survival in the Outer Solar System
- Trans-Neptunian binaries (2018)
- Numerical Simulations of Collisional Disruption of Rotating Gravitational Aggregates: Dependence on Material Properties
- Not a simple relationship between Neptune's migration speed and Kuiper belt inclination excitation
- Lightcurves and Rotational Properties of the Pristine Cold Classical Kuiper Belt Objects
- Distribution of spin-axes longitudes and shape elongations of main-belt asteroids
- Direct -body simulations of satellite formation around small asteroids: insights from DART's encounter with the Didymos system
- A Statistical Review of Light Curves and the Prevalence of Contact Binaries in the Kuiper Belt
- Colors of Trans-Neptunian Contact Binaries
- Dynamical Implantation of Blue Binaries in the Cold Classical Kuiper Belt
- Comets and Planetesimal Formation
- Close TNO Passages as a Driver of the Origin and Evolution of Ultra-Wide Kuiper Belt Binaries
- Superparticle Method for Simulating Collisions
- A Non-Primordial Origin for the Widest Binaries in the Kuiper Belt
- Evolution of Primordial Kuiper Belt Binaries Through a Giant Planet Instability