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Significance The Solar System is an unusual member of the galactic planetary census in that it lacks planets that reside in close proximity to the Sun. In this work, we propose that the primordial nebula-driven process responsible for retention of Jupiter and Saturn at large orbital radii and sculpting Mars’ low mass is also responsible for clearing out the Solar System’s innermost region. Cumulatively, our results place the Solar System and the mechanisms that shaped its unique orbital architecture into a broader, extrasolar context. The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

Surveys of young star-forming regions have discovered a growing population of planetary-mass (<13 M Jup ) companions around young stars 1 . There is an ongoing debate as to whether these companions formed like planets (that is, from the circumstellar disk) 2 , or if they represent the low-mass tail of the star-formation process 3 . In this study, we utilize high-resolution spectroscopy to measure rotation rates of three young (2–300 Myr) planetary-mass companions and combine these measurements with published rotation rates for two additional companions 4 , 5 to provide a picture of the spin distribution of these objects. We compare this distribution to complementary rotation-rate measurements for six brown dwarfs with masses <20 M Jup , and show that these distributions are indistinguishable. This suggests that either these two populations formed via the same mechanism, or that processes regulating rotation rates are independent of formation mechanism. We find that rotation rates for both populations are well below their break-up velocities and do not evolve significantly during the first few hundred million years after the end of accretion. This suggests that rotation rates are set during the late stages of accretion, possibly by interactions with a circumplanetary disk. This result has important implications for our understanding of the processes regulating the angular momentum evolution of young planetary-mass objects, and of the physics of gas accretion and disk coupling in the planetary-mass regime. Similar physical processes regulate the angular momentum of gas-giant planets and planetary-mass brown dwarfs. These processes are active mostly during the early phase of planetary evolution as rotation rates do not change after the first 2–300 Myr.

Modelling shows that the misaligned orbits of ‘hot Jupiters’ can follow naturally from disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars. Orbital disruption of 'hot Jupiter' exoplanets Recent planetary transit observations have shown that many 'hot Jupiter' exoplanets in close-in orbits are grossly misaligned with respect to the rotation axes of their host stars. This fact has cast doubt on a previously widely accepted model of disk-driven migration as the primary mechanism responsible for moving planetrs from an outer to an inner orbit. In this paper Konstantin Batygin demonstrates that disk-driven migration is not only capable of producing misaligned planets, it will produce them preferentially. The argument rests on the observation that most stars are born as binaries, and that the gravitational perturbations of the stellar companions act to twist the orbital planes of proto-planetary disks out of alignment with the rotation axes of their host stars. The existence of gaseous giant planets whose orbits lie close to their host stars (‘hot Jupiters’) can largely be accounted for by planetary migration associated with viscous evolution of proto-planetary nebulae 1 . Recently, observations of the Rossiter–McLaughlin effect 2 during planetary transits have revealed that a considerable fraction of hot Jupiters are on orbits that are misaligned with respect to the spin axes of their host stars 3 . This observation has cast doubt on the importance of disk-driven migration as a mechanism for producing hot Jupiters. Here I show that misaligned orbits can be a natural consequence of disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars 4 , 5 , 6 . The gravitational torques arising from the dynamical evolution of idealized proto-planetary disks under perturbations from massive distant bodies act to misalign the orbital planes of the disks relative to the spin poles of their host stars. As a result, I suggest that in the absence of strong coupling between the angular momentum of the disk and that of the host star, or of sufficient dissipation that acts to realign the stellar spin axis and the planetary orbits, the fraction of planetary systems (including systems of ‘hot Neptunes’ and ‘super-Earths’) whose angular momentum vectors are misaligned with respect to their host stars will be commensurate with the rate of primordial stellar multiplicity.

The formation of super-Earths, the most abundant planets in the Galaxy, remains elusive. These planets have masses that typically exceed that of the Earth by a factor of a few, appear to be predominantly rocky, although often surrounded by H/He atmospheres, and frequently occur in multiples. Moreover, planets that encircle the same star tend to have similar masses and radii, whereas those belonging to different systems exhibit remarkable overall diversity. Here we advance a theoretical picture for rocky planet formation that satisfies the aforementioned constraints: building upon recent work, which has demonstrated that planetesimals can form rapidly at discrete locations in the disk, we propose that super-Earths originate inside rings of silicate-rich planetesimals at approximately ~1 au. Within the context of this picture, we show that planets grow primarily through pairwise collisions among rocky planetesimals until they achieve terminal masses that are regulated by isolation and orbital migration. We quantify our model with numerical simulations and demonstrate that our synthetic planetary systems bear a close resemblance to compact, multi-resonant progenitors of the observed population of short-period extrasolar planets.A planetary origin model that forms exoplanets from a narrow ring of silicate material at a stellocentric distance of 1 au is able to explain the physical properties of super-Earths and reproduce the ‘peas in a pod’ pattern of uniformity within planetary architecture.

The formation of the Inner Oort Cloud (IOC)—a vast halo of icy bodies residing far beyond Neptune’s orbit—is an expected outcome of the solar system’s primordial evolution within a stellar cluster. Recent models have shown that the process of early planetesimal capture within the trans-Neptunian region may have been sufficiently high for the cumulative mass of the Cloud to approach several Earth masses. In light of this, here we examine the dynamical evolution of the IOC, driven by its own self-gravity. We show that the collective gravitational potential of the IOC is adequately approximated by the Miyamoto–Nagai model and use a semi-analytic framework to demonstrate that the resulting secular oscillations are akin to the von Zeipel–Lidov–Kozai resonance. We verify our results with direct N-body calculations and examine the effects of IOC self-gravity on the long-term behavior of the solar system’s minor bodies using a detailed simulation. Cumulatively, we find that while the modulation of perihelion distances and inclinations can occur within an observationally relevant range, the associated timescales vastly surpass the age of the sun, indicating that the influence of IOC self-gravity on the architecture of the solar system is negligible.

Modelling shows that the misaligned orbits of 'hot Jupiters' can follow naturally from disk migration in binary systems whose orbital plane is uncorrelated with the spin axes of the individual stars.

TRAPPIST-1 hosts seven planets. The period ratios of neighbouring pairs are close to the 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2 ratios in increasing distance from the star. The Laplace angles associated with neighbouring triplets are observed to be librating, proving the resonant nature of the system. This compact, resonant configuration is a manifest sign of disk-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. Here, we explain the observed orbital configuration with a model that is largely independent of the specific disk migration and orbital circularization efficiencies. Together with migration, the two key elements of our model are that the inner border of the protoplanetary disk receded with time and that the system was initially separated into two subsystems. Specifically, the inner b, c, d and e planets were initially placed in a 3:2 resonance chain and then evolved to the 8:5–5:3 commensurability between planets b, c and d due to the recession of the inner edge of the disk, whereas the outer planets migrated to the inner edge at a later time and established the remaining resonances. Our results pivot on the dynamical role of the presently unobservable recession of the inner edge of protoplanetary disks. They also reveal the role of recurring phases of convergent migration followed by resonant repulsion with associated orbital circularization when resonant chains interact with migration barriers. The dynamical history of the seven-planet TRAPPIST-1 system, which is marked by delicate orbital resonances, is meticulously reconstructed. This study unveils the key physical processes that shaped its formation during and beyond the circumstellar disk phase.

As a result of resonance overlap, planetary systems can exhibit chaotic motion. Planetary chaos has been studied extensively in the Hamiltonian framework, however, the presence of chaotic motion in systems where dissipative effects are important, has not been thoroughly investigated. Here, we study the onset of stochastic motion in presence of dissipation, in the context of classical perturbation theory, and show that planetary systems approach chaos via a period-doubling route as dissipation is gradually reduced. Furthermore, we demonstrate that chaotic strange attractors can exist in mildly damped systems. The results presented here are of interest for understanding the early dynamical evolution of chaotic planetary systems, as they may have transitioned to chaos from a quasi-periodic state, dominated by dissipative interactions with the birth nebula.

The trans-Neptunian scattered disk exhibits unexpected dynamical structure, ranging from an extended dispersion of perihelion distance to a clustered distribution in orbital angles. Self-gravitational modulation of the scattered disk has been suggested in the literature as an alternative mechanism to Planet 9 for sculpting the orbital architecture of the trans-Neptunian region. The numerics of this hypothesis have hitherto been limited to \\(N < O(10^3)\\) super-particle simulations that omit direct gravitational perturbations from the giant planets and instead model them as an orbit-averaged (quadrupolar) potential, through an enhanced \\(J_2\\) moment of the central body. For sufficiently massive disks, such simulations reveal the onset of collective dynamical behaviour \\(\\unicode{x2014}\\) termed the \\(\\unicode{x2018}\\)inclination instability\\(\\unicode{x2019}\\) \\(\\unicode{x2014}\\) wherein orbital circularisation occurs at the expense of coherent excitation of the inclination. Here, we report \\(N = O(10^4)\\) GPU-accelerated simulations of a self-gravitating scattered disk (across a range of disk masses spanning 5 to 40 Earth masses) that self-consistently account for intra-particle interactions as well as Neptune's perturbations. Our numerical experiments show that even under the most favourable conditions, the inclination instability never ensues. Instead, due to scattering, the disk depletes. While our calculations show that a transient lopsided structure can emerge within the first few hundreds of Myr, the terminal outcomes of these calculations systematically reveal a scattered disk that is free of any orbital clustering. We conclude thus that the inclination instability mechanism is an inadequate explanation of the observed architecture of the solar system.

Short-period super-Earths and mini-Neptunes encircle more than \\(\\sim50\\%\\) of Sun-like stars and are relatively amenable to direct observational characterization. Despite this, environments in which these planets accrete are difficult to probe directly. Nevertheless, pairs of planets that are close to orbital resonances provide a unique window into the inner regions of protoplanetary disks, as they preserve the conditions of their formation, as well as the early evolution of their orbital architectures. In this work, we present a novel approach toward quantifying transit timing variations within multi-planetary systems and examine the near-resonant dynamics of over 100 planet pairs detected by \\textit{Kepler}. Using an integrable model for first-order resonances, we find a clear transition from libration to circulation of the resonant angle at a period ratio of \\(\\approx 0.6\\%\\) wide of exact resonance. The orbital properties of these systems indicate that they systematically lie far away from the resonant forced equilibrium. Cumulatively our modeling indicates that while orbital architectures shaped by strong disk damping or tidal dissipation are inconsistent with observations, a scenario where stochastic stirring by turbulent eddies augments the dissipative effects of protoplanetary disks reproduces several features of the data.