FORMATION OF KUIPER BELT BINARIES BY GRAVITATIONAL COLLAPSE

By D. Nesvorný, A. Youdin, Derek C. Richardson. 2010

209 citations recorded by the source corpus.

A large fraction of ∼100 km class low-inclination objects in the classical Kuiper Belt (KB) are binaries with comparable masses and a wide separation of components. A favored model for their formation is that they were captured during the coagulation growth of bodies in the early KB. However, recent studies have suggested that large, ≳100 km objects can rapidly form in the protoplanetary disks when swarms of locally concentrated solids collapse under their own gravity. Here, we examine the possibility that KB binaries formed during gravitational collapse when the excess of angular momentum prevented the agglomeration of available mass into a solitary object. We find that this new mechanism provides a robust path toward the formation of KB binaries with observed properties, and can explain wide systems such as 2001 QW322 and multiples such as (47171) 1999 TC36. Notably, the gravitational collapse is capable of producing ∼100% binary fraction for a wide range of the swarm's initial angular momentum values. The binary components have similar masses (∼80% have a secondary-over-primary radius ratio >0.7) and their separation ranges from ∼1000 to ∼100,000 km. The binary orbits have eccentricities from e = 0 to ∼1, with the majority having e < 0.6. The binary orbit inclinations with respect to the initial angular momentum of the swarm range from i = 0 to ∼90°, with most cases having i < 50°. The total binary mass represents a characteristic fraction of the collapsing swarm's total initial mass, Mtot, suggesting Mtot equivalent to that of a radius ∼100–250 km compact object. Our binary formation mechanism also implies that the primary and secondary components in each binary pair should have identical bulk composition, which is consistent with the current photometric data. We discuss the applicability of our results to the Pluto–Charon, Orcus–Vanth, (617) Patroclus–Menoetius, and (90) Antiope binary systems.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e1c5cd1eac9d7ffe04717a336b0c3836d89d0994

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In Astronomy and Astrophysics

Citations in the corpus

Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities (2011, methodology): “…picture of the planetesimal formation stage, and at the same time it gives insight into the physical processes that shaped the architectures of these systems (Morbidelli et al. 2009; Weidenschilling 2010; Nesvorný et al. 2010; Sheppard & Trujillo 2010; Krivov 2010; Kenyon & Bromley 2010).”
Dust Evolution and the Formation of Planetesimals (2016, result): “Nesvorný et al. (2010) showed that the collapse typically leads to the formation of binary planetesimals, in good agreement with the prevalence of binaries in the classical cold component of the Kuiper belt (e.g., Noll et al. 2008).”
Building Terrestrial Planets (2012, background): “The existence and the properties of binary Kuiper belt objects also are best explained by the gravitational collapse of massive swarms of small particles that have angular momenta too large to form single objects (Nesvorny et al. 2010b).”
The Compositions of Kuiper Belt Objects (2011, background): “If, alternatively, binary KBOs were formed in an initial gravitational collapse (Nesvorný, Youdin & Richardson 2010), the objects would of necessity have formed at the same location and of the same materials.”
The primordial nucleus of comet 67P/Churyumov-Gerasimenko (2015, methodology): “However, N-body simulations of gravitational collapse of pebble swarms (Nesvorný et al. 2010) indicate that only a fraction of the swarm mass (determined by the angular momentum) is used for building TNO-sized bodies while the rest disperses.”