Production of trans-Neptunian binaries through chaos-assisted capture

Lee, Ernestine A.; Astakhov, Sergey A.; Farrelly, David

doi:10.1111/j.1365-2966.2007.11930.x

Cited by 44 publications

(57 citation statements)

References 143 publications

(379 reference statements)

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“…However, the majority of Kuiper Belt binaries consist of comparable mass companions with wide separations and have too much angular momenta to have formed by the same mechanism. Instead these systems most likely have a dynamical origin like, for example, binary formation by threebody capture, or binary formation aided by dynamical friction (Weidenschilling 2002;Goldreich et al 2002;Funato et al 2004;Astakhov et al 2005;Lee et al 2007). The Hill sphere, the region interior to an object's Hill radius, sets the maximum phase space available for binary formation by such dynamical processes.…”

Section: Implications For Kuiper Belt Binariesmentioning

confidence: 99%

Runaway Growth During Planet Formation: Explaining the Size Distribution of Large Kuiper Belt Objects

Schlichting

Sari

2011

ApJ

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Runaway growth is an important stage in planet formation during which large protoplanets form, while most of the initial mass remains in small planetesimals. The amount of mass converted into large protoplanets and their resulting size distribution are not well understood. Here, we use analytic work, that we confirm by coagulation simulations, to describe runaway growth and the corresponding evolution of the velocity dispersion. We find that runaway growth proceeds as follows. Initially, all the mass resides in small planetesimals, with mass surface density σ , and large protoplanets start to form by accreting small planetesimals. This growth continues until growth by merging large protoplanets becomes comparable to growth by planetesimal accretion. This condition sets in when Σ/σ ∼ α 3/4 ∼ 10 −3 , where Σ is the mass surface density in protoplanets in a given logarithmic mass interval and α is the ratio of the size of a body to its Hill radius. From then on, protoplanetary growth and the evolution of the velocity dispersion become self-similar and Σ remains roughly constant, since an increase in Σ by accretion of small planetesimals is balanced by a decrease due to merging with large protoplanets. We show that this growth leads to a protoplanet size distribution given by N (>R) ∝ R −3 , where N (>R) is the number of objects with radii greater than R (i.e., a differential power-law index of 4). Since only the largest bodies grow significantly during runaway growth, Σ and thereby the size distribution are preserved. We apply our results to the Kuiper Belt, which is a relic of runaway growth where planet formation never proceeded to completion. Our results successfully match the observed Kuiper Belt size distribution, they illuminate the physical processes that shaped it and explain the total mass that is present in large Kuiper Belt objects (KBOs) today. This work suggests that the current mass in large KBOs is primordial and that it has not been significantly depleted. We also predict a maximum mass ratio for Kuiper Belt binaries that formed by dynamical processes of α −1/4 ∼ 10, which explains the observed clustering in binary companion sizes that is seen in the cold classical belt. Finally, our results also apply to growth in debris disks, as long as frequent planetesimal-planetesimal collisions are not important during the growth.

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Section: Implications For Kuiper Belt Binariesmentioning

confidence: 99%

Runaway Growth During Planet Formation: Explaining the Size Distribution of Large Kuiper Belt Objects

Schlichting

Sari

2011

ApJ

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“…In order to find evidence for specific formation scenarios of BMPs, it is therefore essential to take the Kozai evolution of the BMPs into account. For example, typical high-eccentricity BMPs produced in some scenarios such as the expected e > 0.8 in the exchange scenario of Funato et al (2004), or 0.2 e 0.8 in the chaos assisted capture scenario (Lee et al 2007), could be observed with very low eccentricities, either due to the random phase in which they are observed during their Kozai cycle or due to their KCTF evolution which would have circularized their orbit (e.g., Figure 2). Recently, (and after the initial presentation of this manuscript), Petit et al (2008) have reported on the peculiar orbit of the Kuiper Belt binary 2001 QW 322 , with very large SMA but relatively small eccentricity.…”

Section: Kctf Observational Signature and Bmps Formations Scenariomentioning

confidence: 99%

Kozai Cycles, Tidal Friction, and the Dynamical Evolution of Binary Minor Planets

Perets

Naoz

2009

ApJ

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In recent years, many binary minor planets (BMPs) have been discovered in the solar system. Many models have been suggested for their formation, but these encounter difficulties explaining their observed characteristics. Here, we show that secular perturbations by the Sun (Kozai mechanism) fundamentally change the evolution and the initial distribution of BMPs predicted by such models and lead to unique observational signatures. The Kozai mechanism can lead to a large periodic oscillations in the eccentricity and inclination of highly inclined BMP orbits, where we predict such effects to be observable with current accuracy within a few years (e.g., for the binary asteroid Huenna). In addition, the combined effects of the Kozai mechanism and tidal friction (KCTF) drives BMPs into short-period circular orbits. We predict a specific inclination-dependent distribution of the separation and eccentricity of BMPs, due to these effects, including a zone of avoidance at the highest inclinations. Specifically, the Kozai evolution could explain the recently observed peculiar orbit of the Kuiper Belt binary 2001 QW 322 . Additionally, the KCTF process could lead to BMPs coalescence and serve as an important route for the formation of irregular shaped single minor planets with large axial tilts.

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“…However, the majority of observed binary KBOs are roughly equal-mass, wide-separation binaries (Noll et al 2008b) that have too much angular momentum to be formed by the same mechanism. Motivated by this challenge, a series of new binary formation scenarios was proposed (e.g., Weidenschilling 2002;Goldreich et al 2002;Funato et al 2004;Astakhov et al 2005;Lee et al 2007;Nesvorný et al 2010). Most of these scenarios appeal to interactions within the Hill sphere, the region interior to the Hill radius of a KBO.…”

Section: Binary Formation Scenariosmentioning

confidence: 99%

Using Kuiper Belt Binaries to Constrain Neptune's Migration History

Murray-Clay¹,

Schlichting²

2011

ApJ

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Approximately 10%-20% of all Kuiper Belt objects (KBOs) occupy mean-motion resonances with Neptune. This dynamical configuration likely resulted from resonance capture as Neptune migrated outward during the late stages of planet formation. The details of Neptune's planetesimal-driven migration, including its radial extent and the concurrent eccentricity evolution of the planet, are the subject of considerable debate. Two qualitatively different proposals for resonance capture have been proposed-migration-induced capture driven by smooth outward evolution of Neptune's orbit and chaotic capture driven by damping of the planet's eccentricity near its current semi-major axis. We demonstrate that the distribution of comparable-mass, wide-separation binaries occupying resonant orbits can differentiate between these two scenarios. If migration-induced capture occurred, this fraction records information about the formation locations of different populations of KBOs. Chaotic capture, in contrast, randomizes the orbits of bodies as they are placed in resonance. In particular, if KBO binaries are formed by dynamical capture in a protoplanetary disk with a surface mass density typical of observed extrasolar disks, then migration-induced capture produces the following signatures. The 2:1 resonance should contain a dynamically cold component, with inclinations less than 5• -10• , having a binary fraction comparable to that among cold classical KBOs. If the 3:2 resonance also hosts a cold component, its binary fraction should be 20%-30% lower than in the cold classical belt. Among cold 2:1 (and if present 3:2) KBOs, objects with eccentricities e < 0.2 should have a binary fraction ∼20% larger than those with e > 0.2. Other binary formation scenarios and disk surface density profiles can generate analogous signatures but produce quantitatively different results. Searches for cold components in the binary fractions of resonant KBOs are currently practical. The additional migration-generated trends described here may be distinguished with objects discovered by LSST.

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Production of trans-Neptunian binaries through chaos-assisted capture

Cited by 44 publications

References 143 publications

Runaway Growth During Planet Formation: Explaining the Size Distribution of Large Kuiper Belt Objects

Runaway Growth During Planet Formation: Explaining the Size Distribution of Large Kuiper Belt Objects

Kozai Cycles, Tidal Friction, and the Dynamical Evolution of Binary Minor Planets

Using Kuiper Belt Binaries to Constrain Neptune's Migration History

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