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We have searched the four brightest objects in the Kuiper Belt for the presence of satellites using the newly commissioned Keck Observatory Laser Guide Star Adaptive Optics system. Satellites are seen around three of the four objects: Pluto (whose satellite Charon is well-known and whose recently discovered smaller satellites are too faint to be de...

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... There are six (or seven) known trans-Neptunian objects (TNOs) with diameters larger than 1000 km, and (almost) all of them host one or more satellites orbiting the primary (e.g., Brown et al. 2006;Parker et al. 2016;Kiss et al. 2017). 1 The discovery of satellites around large TNOs provided us with a key to understanding the early history of the outer solar system. ...
Preprint
Recent astronomical observations revealed that (225088) Gonggong, a 1000-km-sized trans-Neptunian dwarf planet, hosts an eccentric satellite, Xiangliu, with an eccentricity of approximately 0.3. As the majority of known satellite systems around trans-Neptunian dwarf planets have circular orbits, the observed eccentricity of Gonggong--Xiangliu system may reflect the singular properties of the system. In this study, we assumed that Gonggong--Xiangliu system formed via a giant impact and investigated the following secular tidal evolution of Gonggong--Xiangliu system under the simplifying assumption of homogeneous bodies and of zero orbital inclination. We conducted coupled thermal--orbital evolution simulations using the Andrade viscoelastic model and included higher-order eccentricity functions. The distribution of the final eccentricity from a large number of simulations with different initial conditions revealed that the radius of Xiangliu is not larger than 100 km. We also derived the analytical solution of the semilatus rectum evolution, a function of the radius of Xiangliu. From the point of view of the final semilatus rectum, the radius of Xiangliu was estimated to be close to 100 km. Together with the results of the Hubble Space Telescope observations, our findings suggest Gonggong and Xiangliu have similar albedos.
... Surviving impact-generated systems would be expected to vary depending on the specifics of individual collisions (e.g., Arakawa et al., 2019). Differences in impact angle and/or velocity between two like-sized dwarf planets can lead to larger ice/rock fractionations (Barr and Schwamb, 2016), e.g., leading possibly to Eris-Dysnomia (Brown et al., 2006;Greenberg and Barnes, 2008) and Orcus-Vanth ; or outcomes other than a binary (Brown et al., 2006;Canup, 2011), such as Haumea, which only has small moons and a collisional family (Leinhardt et al., 2010). Although the orbit, masses, and compositions of Pluto-Charon strongly implicate an impact origin, those of other binary systems could be compatible with alternative origins (Fig. 2). ...
... Surviving impact-generated systems would be expected to vary depending on the specifics of individual collisions (e.g., Arakawa et al., 2019). Differences in impact angle and/or velocity between two like-sized dwarf planets can lead to larger ice/rock fractionations (Barr and Schwamb, 2016), e.g., leading possibly to Eris-Dysnomia (Brown et al., 2006;Greenberg and Barnes, 2008) and Orcus-Vanth ; or outcomes other than a binary (Brown et al., 2006;Canup, 2011), such as Haumea, which only has small moons and a collisional family (Leinhardt et al., 2010). Although the orbit, masses, and compositions of Pluto-Charon strongly implicate an impact origin, those of other binary systems could be compatible with alternative origins (Fig. 2). ...
Preprint
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The goal of this chapter is to review hypotheses for the origin of the Pluto system in light of observational constraints that have been considerably refined over the 85-year interval between the discovery of Pluto and its exploration by spacecraft. We focus on the giant impact hypothesis currently understood as the likeliest origin for the Pluto-Charon binary, and devote particular attention to new models of planet formation and migration in the outer solar system. We discuss the origins conundrum posed by the system's four small moons. We also elaborate on the implications of these scenarios for the dynamical environment of the early transneptunian disk, the likelihood of finding a Pluto collisional family, and the origin of other binary systems in the Kuiper belt. Finally, we highlight outstanding open issues regarding the origins of the Pluto system and suggest areas of future progress.
... Several trans-Neptunian and Kuiper Belt objects (which we will collectively refer to as TNOs) have recently been found with relatively massive satellite(s). Besides Pluto and Charon, which we discuss in detail, some examples include Eris and Dysnomia (Brown et al. , 2006; Haumea, Hi'iaka, and Namaka (Bouchez et al. 2005); Orcus and Vanth (Brown & Suer 2007); Makemake and MK2 (Parker et al. 2016); Gonggong and Xiangliu (Kiss et al. 2017); and potentially a newly discovered satellite of Varuna (Fernández-Valenzuela et al. 2019). The compactness of these binary systems substantially increases their tidal susceptibility and in some cases has distinctly slowed their rotation rates (e.g., Kiss et al. 2017). ...
Article
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Using the Andrade-derived Sundberg–Cooper rheology, we apply several improvements to the secular tidal evolution of TRAPPIST-1e and the early history of Pluto–Charon under the simplifying assumption of homogeneous bodies. By including higher-order eccentricity terms (up to and including e ²⁰ ), we find divergences from the traditionally used e ² truncation starting around e = 0.1. Order-of-magnitude differences begin to occur for e > 0.6. Critically, higher-order eccentricity terms activate additional spin–orbit resonances. Worlds experiencing nonsynchronous rotation can fall into and out of these resonances, altering their long-term evolution. Nonzero obliquity generally does not generate significantly higher heating; however, it can considerably alter orbital and rotational evolution. Much like eccentricity, obliquity can activate new tidal modes and resonances. Tracking the dual-body dissipation within Pluto and Charon leads to faster evolution and dramatically different orbital outcomes. Based on our findings, we recommend future tidal studies on worlds with e ≥ 0.3 to take into account additional eccentricity terms beyond e ² . This threshold should be lowered to e > 0.1 if nonsynchronous rotation or nonzero obliquity is under consideration. Due to the poor convergence of the eccentricity functions, studies on worlds that may experience very high eccentricity ( e ≥ 0.6) should include terms with high powers of eccentricity. We provide these equations up to e ¹⁰ for arbitrary obliquity and nonsynchronous rotation. Finally, the assumption that short-period, solid-body exoplanets with e ≳ 0.1 are tidally locked in their 1:1 spin–orbit resonance should be reconsidered. Higher-order spin–orbit resonances can exist even at these relatively modest eccentricities, while previous studies have found such resonances can significantly alter stellar-driven climate.
... Several Trans-Neptunian and Kuiper belt objects (which we will collectively refer to as TNOs) have recently been found with relatively massive satellite(s). Besides Pluto and Charon, which we discuss in detail, some examples include Eris & Dysnomia (Brown et al. , 2006, Haumea, Hi'iaka, & Namaka (Bouchez et al. 2005), Orcus & Vanth (Brown & Suer 2007), Makemake & MK2 (Parker et al. 2016), Gonggong & Xiangliu (Kiss et al. 2017), and potentially a newly discovered satellite of Varuna (Fernández-Valenzuela et al. 2019). The compactness of these binary systems substantially increases their tidal susceptibility, and in some cases has distinctly slowed their rotation rates (e.g., Kiss et al. 2017). ...
Preprint
Full-text available
Using the Andrade-derived Sundberg-Cooper rheology, we apply several improvements to the secular tidal evolution of TRAPPIST-1e and the early history of Pluto-Charon under the simplifying assumption of homogeneous bodies. By including higher-order eccentricity terms (up to and including $e^{20}$), we find divergences from the traditionally used $e^{2}$ truncation starting around $e=0.1$. Order-of-magnitude differences begin to occur for $e>0.6$. Critically, higher-order eccentricity terms activate additional spin-orbit resonances. Worlds experiencing non-synchronous rotation can fall into and out of these resonances, altering their long-term evolution. Non-zero obliquity generally does not generate significantly higher heating; however, it can considerably alter orbital and rotational evolution. Much like eccentricity, obliquity can activate new tidal modes and resonances. Tracking the dual-body dissipation within Pluto and Charon leads to faster evolution and dramatically different orbital outcomes. Based on our findings, we recommend future tidal studies on worlds with $e\geq0.3$ to take into account additional eccentricity terms beyond $e^{2}$. This threshold should be lowered to $e>0.1$ if non-synchronous rotation or non-zero obliquity is under consideration. Due to the poor convergence of the eccentricity functions, studies on worlds that may experience very high eccentricity ($e\geq0.6$) should include terms with high powers of eccentricity. We provide these equations up to $e^{10}$ for arbitrary obliquity and non-synchronous rotation. Finally, the assumption that short-period, solid-body exoplanets with $e\gtrsim0.1$ are tidally locked in their 1:1 spin-orbit resonance should be reconsidered. Higher-order spin-orbit resonances can exist even at these relatively modest eccentricities, while previous studies have found such resonances can significantly alter stellar-driven climate.
... The dwarf planet Haumea has two satellites, thought to have formed in a giant impact (e.g., Brown et al. 2006), and its own ring system Winter et al. 2019). In addition, it is the largest object in the first detected collisional family in the trans-Neptunian region (e.g., Brown et al. 2007;Schlichting & Sari 2009;Leinhardt et al. 2010;Lykawka et al. 2012;Volk & Malhotra 2012;Vilenius et al. 2018;Proudfoot & Ragozzine 2019). ...
Article
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Over the past three decades, we have witnessed one of the great revolutions in our understanding of the cosmos—the dawn of the Exoplanet Era. Where once we knew of just one planetary system (the solar system), we now know of thousands, with new systems being announced on a weekly basis. Of the thousands of planetary systems we have found to date, however, there is only one that we can study up-close and personal—the solar system. In this review, we describe our current understanding of the solar system for the exoplanetary science community—with a focus on the processes thought to have shaped the system we see today. In section one, we introduce the solar system as a single well studied example of the many planetary systems now observed. In section two, we describe the solar system's small body populations as we know them today—from the two hundred and five known planetary satellites to the various populations of small bodies that serve as a reminder of the system's formation and early evolution. In section three, we consider our current knowledge of the solar system's planets, as physical bodies. In section four we discuss the research that has been carried out into the solar system's formation and evolution, with a focus on the information gleaned as a result of detailed studies of the system's small body populations. In section five, we discuss our current knowledge of planetary systems beyond our own—both in terms of the planets they host, and in terms of the debris that we observe orbiting their host stars. As we learn ever more about the diversity and ubiquity of other planetary systems, our solar system will remain the key touchstone that facilitates our understanding and modeling of those newly found systems, and we finish section five with a discussion of the future surveys that will further expand that knowledge.
... The richest sample of binary objects within the scope of planetary sciences is in the population of minor solar system bodies. Examples can be found among the near-Earth objects (NEOs; e.g., Margot et al. 2002;Pravec et al. 2006;Scheeres et al. 2006), main-belt asteroids (MBAs; e.g., Marchis et al. 2008;Pravec et al. 2012), Jovian Trojans (e.g., Marchis et al. 2006;Sonnett et al. 2015), and surprisingly frequently among the Kuiper-belt objects (KBOs; e.g., Veillet et al. 2002;Brown et al. 2006;Richardson & Walsh 2006;Noll et al. 2008). Formation of binary minor bodies took place during various epochs of the solar system. ...
Article
We present radiation hydrodynamic simulations in which binary planets form by close encounters in a system of several super-Earth embryos. The embryos are embedded in a protoplanetary disk consisting of gas and pebbles and evolve in a region where the disk structure supports convergent migration due to Type I torques. As the embryos accrete pebbles, they become heated and thus affected by the thermal torque and the hot-trail effect, which excites orbital eccentricities. Motivated by findings of Eklund & Masset, we assume that the hot-trail effect also operates vertically and reduces the efficiency of inclination damping. Non-zero inclinations allow the embryos to become closely packed and also vertically stirred within the convergence zone. Subsequently, close encounters of two embryos assisted by the disk gravity can form transient binary planets that quickly dissolve. Binary planets with a longer lifetime of ~10⁴ yr form in three-body interactions of a transient pair with one of the remaining embryos. The separation of binary components generally decreases in subsequent encounters and because of pebble accretion until the binary merges, forming a giant planet core. We provide an order-of-magnitude estimate of the expected occurrence rate of binary planets, yielding one binary planet per (2–5) × 10⁴ planetary systems. Therefore, although rare, binary planets may exist in exoplanetary systems and they should be systematically searched for.
... Marchis et al. 2006;Sonnett et al. 2015) and surprisingly frequently among the Kuiper-belt objects (KBOs; e.g. Veillet et al. 2002;Brown et al. 2006;Richardson & Walsh 2006;Noll et al. 2008). Formation of binary minor bodies took place during various epochs of the Solar System. ...
Preprint
We present radiation hydrodynamic simulations in which binary planets form by close encounters in a system of several super-Earth embryos. The embryos are embedded in a protoplanetary disk consisting of gas and pebbles and evolve in a region where the disk structure supports convergent migration due to Type I torques. As the embryos accrete pebbles, they become heated and thus affected by the thermal torque (Ben\'{i}tez-Llambay et al. 2015) and the hot-trail effect (Chrenko et al. 2017) which excites orbital eccentricities. Motivated by findings of Eklund & Masset (2017), we assume the hot-trail effect operates also vertically and reduces the efficiency of inclination damping. Non-zero inclinations allow the embryos to become closely packed and also vertically stirred within the convergence zone. Subsequently, close encounters of two embryos assisted by the disk gravity can form transient binary planets which quickly dissolve. Binary planets with a longer lifetime $\sim$$10^{4}$ yr form in 3-body interactions of a transient pair with one of the remaining embryos. The separation of binary components generally decreases in subsequent encounters and due to pebble accretion until the binary merges, forming a giant planet core. We provide an order-of-magnitude estimate of the expected occurrence rate of binary planets, yielding one binary planet per $\simeq$$2$--$5\times10^{4}$ planetary systems. Therefore, although rare, the binary planets may exist in exoplanetary systems and they should be systematically searched for.
... During the approach to Ultima, we will conduct a deep search for small satellites and rings with the LORRI camera. Small satellites have previously been detected around several KBOs (e.g., Brown et al., 2006;Stephens and Noll, 2006;Parker et al., 2016;Kiss et al., 2017), Centaurs (10199) Chariklo and (2060) Chiron, and dwarf planet Haumea have rings (Braga-Ribas et al., 2014;Ortiz et al., 2015Ortiz et al., , 2017, and the moderately-sized (47171) Lempo is a hierarchical triple system (Bennechi et al., 2010). ...
Article
The New Horizons encounter with the cold classical Kuiper Belt object (KBO) 2014 MU69 (informally named 'Ultima Thule,' hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the Kuiper Belt. Related to but not thought to have formed in the same region of the Solar System as the comets that been explored so far, it will also be the largest, most distant, and most primitive body yet visited by spacecraft. In this letter we begin with a brief overview of cold classical KBOs, of which Ultima is a prime example. We give a short preview of our encounter plans. We note what is currently known about Ultima from earth-based observations. We then review our expectations and capabilities to evaluate Ultima's composition, surface geology, structure, near space environment, small moons, rings, and the search for activity.
... For example, the so-called "Planet Nine" is believed to have a high inclination and high eccentricity (Brown and Batygin, 2016) yet would not be debarred from the planet taxon on that basis. Herschel's argument about moons was incorrect, because we now know there are very many asteroids with moons (e.g., Merline et al., 2002) and KBOs with moons (e.g., Christy and Harrington, 1980;Brown et al., 2006). Herschel's argument about comas of asteroids was based on an observational error, but even if it were not an error the existence of a large atmosphere is not considered a debarring property from the planet taxon. ...
Preprint
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It is often claimed that asteroids' sharing of orbits is the reason they were re-classified from planets to non-planets. A critical review of the literature from the 19th Century to the present shows this is factually incorrect. The literature shows the term asteroid was broadly recognized as a subclass of planet for 150 years. On-going discovery of asteroids resulted in a de facto stretching of the concept of planet to include the ever smaller bodies. Scientists found utility in this taxonomic identification as it provided categories needed to argue for the leading hypothesis of planet formation, Laplace's nebular hypothesis. In the 1950s, developments in planet formation theory found it no longer useful to maintain taxonomic identification between asteroids and planets, Ceres being the sole exception. At approximately the same time, there was a flood of publications on the geophysical nature of asteroids showing them to be geophysically different than the large planets. This is when the terminology in asteroid publications calling them planets abruptly plunged from a high level of usage where it had hovered during the period 1801 - 1957 to a low level that held constant thereafter. This marks the point where the community effectively formed consensus that asteroids should be taxonomically distinct from planets. The evidence demonstrates this consensus formed on the basis of geophysical differences between asteroids and planets, not the sharing of orbits. We suggest attempts to build consensus around planetary taxonomy not rely on the non-scientific process of voting, but rather through precedent set in scientific literature and discourse, by which perspectives evolve with additional observations and information, just as they did in the case of asteroids.
... Ainsi, il est très probable que les satellites des grands objets aient été formés par une collision. Par exemple, les études sur les satellites de Hauméa et Eris (Brown et al., 2006) Les classes dynamiques sont désignés par des couleurs : rouge -objets classiques chauds, bleuobjets classiques froids, verts -objets épars, violet -détachés, noir -plutinos, orange -objets en résonance avec Neptune. été réalisé par la capture gravitationnelle des objets. ...
Thesis
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Cette thèse est consacrée à l'étude des objets binaires du Système solaire selon deux axes principaux. Premièrement, nous examinons les paramètres physiques, tels que la taille et l'albédo des binaires transneptuniens, obtenus à partir des mesures de flux thermique en infrarouge par les télescopes spatiaux Herschel et Spitzer. Avec ces paramètres, nous comparons les objets binaires avec les transneptuniens sans satellite. Cette analyse montre que les distributions de tailles dans les deux populations sont différentes. Nous supposons que cette tendance est liée à la prépondérance des petits binaires dans le groupe des objets "froide", qui est plus favorable à la survie des binaires, parmi les autre groupes.De plus, nous étudions les corrélations entre la taille et l'albédo et d'autres paramètres physiques et orbitaux pour la population des binaires. Cette étude montre les fortes corrélations suivantes: entre la taille et la masse, la taille et l'inclinaison héliocentrique, la taille et la différence de magnitudes des composantes. L'étude trouve également deux corrélations moins significatives -- la densité avec la taille et la densité avec l'albédo -- qui nécessitent des vérifications ultérieures avec des données complémentaires. Nous donnons une interprétation possible des résultats du point de vue des différents modèles de formation de tels objets.Deuxièmement, nous présentons une nouvelle méthode de détermination d'orbite mutuelle d'un système binaire. Cette méthode est basée sur la technique de Monte-Carlo par chaînes de Markov avec une approche bayésienne. L'algorithme, développé dans cette thèse, permet de déterminer où d'ajuster les paramètres d'une orbite képlérienne ou d'une orbite perturbée à partir des observations simulées et réelles. Nous montrons que la méthode peut être efficace même pour un petit nombre d'observations et sans condition initiale particulière.