Gravitational Capture of Large Interstellar Planetesimals by Collapsing Prestellar Cores
Authors: Richard Anderson, Kedron Silsbee
Abstract
We investigate the capture of free-floating planetesimals by the time-varying gravitational potential of a collapsing prestellar core. We use one-dimensional collapse models to estimate the volume of space from which planetesimals are captured. We combine this calculation with an estimate of the size distribution and velocity dispersion of the free-floating planetesimal population to determine the largest planetesimal that is typically captured, as well as the total mass of all planetesimals captured by a given protostar. We consider two cases: one in which the free-floating planetesimal population comes from the birth cluster of the star, and one in which the planetesimals are captured from the Galactic population of free-floating planetesimals. We find that the details of the collapse matter substantially, with the predicted diameter of the largest captured body from the Galactic population ranging from $2.8$ km to $6.4$ km depending on collapse model, and the largest body from our model birth cluster environment ranging from $70$ km to $1200$ km, for assumed velocity dispersions ranging from 0.7 to 8.5 km/s. The total solid mass captured by this mechanism does not exceed 0.07 Earth masses in all cases. We discuss the effect of these captured objects on the planet formation process, and argue that while the total solid mass captured is likely not significant, the largest captured bodies may grow to planet size via accretion of pebbles present in their host disks. This process may accelerate planet formation, or enable it in disks that have difficulty in forming their own planetesimals.
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Closest papers
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Capture of Interstellar Planetesimals in Protoplanetary Discs in Binary Star SystemsAlia Pollard, E. Grishin · 2026 · Monthly notices of the Royal Astronomical Society · Not summarized yet
Abstract
Planet formation requires growth over 12 orders of magnitude in size, from micron-sized dust grains to fully formed planets. The formation of $\sim \rm km$ sized planetesimals is the most challenging stage, where radial drift and fragmentation rapidly remove meter-sized solids from the protoplanetary disc. Overcoming this barrier requires favourable conditions for streaming instability to concentrate solids. These problems are exacerbated in binary star systems, where gravitational perturbations and disc truncation reduce the efficiency of planetesimal formation pathways. Planetesimal capture provides an alternative mechanism where unbound planetesimals are captured by the protoplanetary dis…
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Planet seeding through gas-assisted capture of interstellar objectsE. Grishin, H. Perets, Yael Avni · 2018 · Monthly notices of the Royal Astronomical Society · cited 23 times · Not summarized yet
Abstract
Planet formation begins with collisional growth of small planetesimals accumulating into larger ones. Such growth occurs while planetesimals are embedded in a gaseous protoplanetary disc. However, small-planetesimals experience collisions and gas-drag that lead to their destruction on short timescales, not allowing, or requiring fine tuned conditions for the efficient growth of $\sim$ metre-size objects. Here we show that $\sim10^{4}$ interstellar objects such as the recently detected 1I/2017-U1 ('Oumuamua) could have been captured, and become part of the young Solar System, together with up to hundreds of $\sim$ km sized ones. The capture rates are robust even for conservative assumptions o…
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Interstellar Planetesimals: Potential Seeds for Planet Formation?A. Moro-Martín, C. Norman · 2021 · Astrophysical Journal · cited 8 times · Not summarized yet
Abstract
We investigate the trapping of interstellar objects during the early stages of star and planet formation. Our results show a very wide range of possible values that will be narrowed down as the population of interstellar objects becomes better characterized. When assuming a background number density of 2 · 1015 pc−3 (based on 1I’s detection), a velocity dispersion of 30 km s−1, and an equilibrium size distribution, the number of interstellar objects captured by a molecular cloud and expected to be incorporated to each protoplanetary disk during its formation is O(109) (50 cm–5 m), O(105) (5–50 m), O(102) (50–500 m), O(10−2) (500 m–5 km). After the disk has formed, the number of interstellar …
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Understanding the trans-Neptunian Solar system: Reconciling the results of serendipitous stellar occultations and the inferences from the cratering recordAndrew Shannon, Alain Doressoundiram, Françoise Roques et al. · 2021 · Earth and Planetary Astrophysics · cited 4 times · Not summarized yet
Abstract
The most pristine remnants of the Solar system's planet formation epoch orbit the Sun beyond Neptune, the small bodies of the trans-Neptunian object populations. The bulk of the mass is in ~100 km objects, but objects at smaller sizes have undergone minimal collisional processing, with New Horizons recently revealing that ~20 km effective diameter body (486958) Arrokoth appears to be a primordial body, not a collisional fragment. This indicates bodies at these sizes (and perhaps smaller) retain a record of how they were formed, and are the most numerous record of that epoch. However, such bodies are impractical to find by optical surveys due to their very low brightnesses. Their presence can…
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Rapid growth of gas-giant cores by pebble accretionM. Lambrechts, A. Johansen · 2012 · Astronomy and Astrophysics · cited 669 times · Not summarized yet
Abstract
The observed lifetimes of gaseous protoplanetary discs place strong constraints on gas and ice giant formation in the core accretion scenario. The approximately 10-Earth-mass solid core responsible for the attraction of the gaseous envelope has to form before gas dissipation in the protoplanetary disc is completed within 1–10 million years. Building up the core by collisions between km-sized planetesimals fails to meet this timescale constraint, especially at wide stellar separations. Nonetheless, gas-giant planets are detected by direct imaging at wide orbital distances. In this paper, we numerically study the growth of cores by the accretion of cm-sized pebbles loosely coupled to the gas. …
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Collisional Evolution around A-type Stars with Strong Silicate FeaturesT. A. Stuber, H. Kobayashi, S. Wolf et al. · 2026 · Earth and Planetary Astrophysics · AI summary available
Abstract
Around luminous A-type stars, retaining micrometer-sized dust grains is difficult owing to the high radiation pressure that repels particles with sizes below the blowout limit. Yet such particles have been evidenced in the terrestrial zone around those stars, via pronounced silicate spectral features. An in situ planetesimal belt that collisionally replenishes the dust is expected to deplete quickly, limiting the lifetime of observable features. However, modeling of such systems often relies on a power-law description of the grain size distribution that has a lower size limit owing to blowout. Using more complex, collisional simulations instead, we investigated the temporal evolution of hypo…
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Giant planet engulfment by evolved giant stars: light curves, asteroseismology, and survivabilityChristopher E. O'Connor, Lars Bildsten, Matteo Cantiello et al. · 2023 · Earth and Planetary Astrophysics · cited 20 times · AI summary available
Abstract
About ten percent of Sun-like ($1$-$2 M_\odot$) stars will engulf a $1$-$10 M_{\rm J}$ planet as they expand during the red giant branch (RGB) or asymptotic giant branch (AGB) phase of their evolution. Once engulfed, these planets experience a strong drag force in the star's convective envelope and spiral inward, depositing energy and angular momentum. For these mass ratios, the inspiral takes $\sim 10$-$10^{2}$ years ($\sim 10^{2}$-$10^{3}$ orbits); the planet undergoes tidal disruption at a radius of $\sim R_\odot$. We use the Modules for Experiments in Stellar Astrophysics (MESA) software instrument to track the stellar response to the energy deposition while simultaneously evolving the p…
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Beyond Pebble Isolation: Diverse Pathways to Giant Planet Formation Across Stellar and Orbital ScalesLorenzo Peerani, S. Shibata, R. Helled · 2026 · Not summarized yet
Abstract
Context. Giant planet formation requires reaching crossover mass, i.e., when the mass of the gaseous envelope becomes equal to the mass of the core, within the disc's lifetime. The formation process depends critically on the orbital distance and stellar mass. Aims. We simulate planet formation via pebble accretion up to crossover mass around stellar hosts with masses of 0.1-1.5 Msun, considering a range of formation locations, with and without Type I migration. Methods. We use a modified version of MESA that couples pebble accretion, gas accretion, and disc evolution. Results. We find that cold/warm Jupiters form, whereas in-situ formation fails at short orbital separations: viscous heating …
Prior work it builds on
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Numerical Calculations of the Dynamics of a Collapsing Proto-StarR. Larson · 1969 · Monthly Notices of the Royal Astronomical Society · cited 1,212 times · Not summarized yet
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Self-similar collapse of isothermal spheres and star formation.F. Shu · 1977 · The Astrophysical Journal · cited 1,354 times · Not summarized yet
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A Hypothesis for the Rapid Formation of PlanetsS. Pfalzner, M. Bannister · 2019 · Astrophysical Journal · cited 28 times · Not summarized yet
Abstract
The discovery of 1I/‘Oumuamua confirmed that planetesimals must exist in great numbers in interstellar space. Originally generated during planet formation, they are scattered from their original systems and subsequently drift through interstellar space. As a consequence they should seed molecular clouds with at least hundred-meter-scale objects. We consider how the galactic background density of planetesimals, enriched from successive generations of star and system formation, can be incorporated into forming stellar systems. We find that at a minimum of the order of 107 ‘Oumuamua-sized and larger objects, plausibly including hundred-kilometer-scale objects, should be present in protoplanetar…
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Interstellar Interlopers: Number Density and Origin of ‘Oumuamua-like ObjectsA. Do, M. Tucker, J. Tonry · 2018 · The Astrophysical Journal Letters · cited 120 times · Not summarized yet
Abstract
We provide a calculation of Pan-STARRS’ ability to detect objects similar to the interstellar object 1I/2017 U1 (hereafter ‘Oumuamua), including the most detectable approach vectors and the effect of object size on detection efficiency. Using our updated detection cross section, we infer an interstellar number density of such objects ( ). This translates to a mass density of that cannot be populated unless every star is contributing. We find that, given current models, such a number density cannot arise from the ejection of inner solar system material during planet formation. We note that a stellar system’s Oort cloud will be released after a star’s main-sequence life time and may provide en…
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Formation of dust-rich planetesimals from sublimated pebbles inside of the snow lineS. Ida, T. Guillot · 2016 · Astronomy and Astrophysics · cited 84 times · Not summarized yet
Abstract
Context. For up to a few millions of years, pebbles must provide a quasi-steady inflow of solids from the outer parts of protoplanetary disks to their inner regions. Aims. We wish to understand how a significant fraction of the pebbles grows into planetesimals instead of being lost to the host star. Methods. We examined analytically how the inward flow of pebbles is affected by the snow line and under which conditions dust-rich (rocky) planetesimals form. When calculating the inward drift of solids that is due to gas drag, we included the back-reaction of the gas to the motion of the solids. Results. We show that in low-viscosity protoplanetary disks (with a monotonous surface density simila…
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