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Title: Properties of the Distant Kuiper Belt: Results from the Palomar Distant Solar System Survey
Authors: Megan E. Schwamb, Michael E. Brown, David L. Rabinowitz, Darin Ragozzine

We present the results of a wide-field survey using the 1.2-m Samuel Oschin Telescope at Palomar Observatory. This survey was designed to find the most distant members of the Kuiper belt and beyond. We searched ~12,000 deg2 down to a mean limiting magnitude of 21.3 in R. A total number of 52 KBOs and Centaurs have been detected, 25 of which were discovered in this survey. Except for the re-detection of Sedna, no additional Sedna-like bodies with perihelia greater than 45 AU were detected despite sensitivity out to distances of 1000 AU. We discuss the implications for a distant Sedna- like population beyond the Kuiper belt, focusing on the constraints we can place on the embedded stellar cluster environment the early Sun may be have been born in, where the location and distribution of Sedna-like orbits sculpted by multiple stellar encounters is indicative of the birth cluster size. We also report our observed latitude distribution and implications for the size of the plutino population.

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Title: Formation of Kuiper Belt Binaries by Gravitational Collapse
Authors: David Nesvorny, Andrew N. Youdin, Derek C. Richardson

A large fraction of 100-km-class low-inclination objects in the classical Kuiper Belt (KB) are binaries with comparable mass and wide separation of components. A favoured model for their formation was capture during the coagulation growth of bodies in the early KB. Instead, recent studies suggested that large 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 the secondary-over-primary radius ratio >0.7) and their separation ranges from ~1,000 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 deg, with most cases having i<50 deg. Our binary formation mechanism 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.

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Smallest Kuiper Belt object
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Smallest object in outer solar system spotted

In a cosmic version of the old needle-in-a-haystack finding, astronomers have spotted an object less than a mile wide that is 4.2 billion miles away, in the outer solar system.
The object is part of the Kuiper Belt, an ring of icy rocks beyond Neptune. The object, spotted in visible light by the Hubble Space Telescope, is about 3,200 feet (975 meters) across.
Previously, the smallest object seen via reflected visible light in the Kuiper Belt was 30 miles wide.

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Solar System Icy Bodies
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Title: Icy Bodies in the New Solar System
Authors: David Jewitt

This brief paper summarizes a "key general review" with the same title given at the IAU meeting in Rio de Janeiro. The intent of the review talk was to give a broad and well-illustrated overview of recent work on the icy middle and outer Solar system, in a style interesting for those astronomers whose gaze is otherwise drawn to more distant realms. The intent of this written review is the same.

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Taking the Kuiper Belt Census

Q&A: Lowell Observatory astronomer Larry Wasserman has been taking a headcount of ancient KBOs. Why? To understand the origins of our solar system.
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Kuiper Belt Objects
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Title: The Sizes of Kuiper Belt Objects
Authors: Pedro Lacerda

One of the most fundamental problems in the study of Kuiper belt objects (KBOs) is to know their true physical size. Without knowledge of their albedos we are not able to distinguish large and dark from small and bright KBOs. Spitzer produced rough estimates of the sizes and albedos of about 20 KBOs, and the Herschel space telescope will improve on those initial measurements by extending the sample to the ~150 brightest KBOs. SPICA's higher sensitivity instruments should allow us not only to broaden the sample to smaller KBOs but also to achieve a statistically significant sample of KBO thermal light curves (Herschel will measure only six objects). A large sample covering a broad range of sizes will be key to identify meaningful correlations between size and other physical and surface properties that constrain the processes of formation and evolution of the solar system.

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Kuiper Belt Objects
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Title: From KBOs to Centaurs: The Thermal Connection
Authors: G. Sarid, D. Prialnik

We present results of thermal evolution calculations for objects originating in the Kuiper belt and transferring inwards, to the region of the outer planets. Kuiper belt objects (KBOs) are considered to be part of a reservoir that supplies the flux of small icy bodies, mainly Centaurs and Jupiter-family comets, to regions interior to the orbit of Neptune. We study the internal thermal evolution, for yr, of three typical KBOs and use the end state of the simulation as initial conditions for evolutionary calculations of two typical Centaurs. Some evolutionary trends can be identified for the KBOs, depending on key physical parameters, such as size and composition. The subsequent evolution in the Centaur region results in both specific features for each modelled object (mainly surface and sub-surface composition) and common characteristics of thermally evolved Centaurs.

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Title: Chaotic Diffusion of Resonant Kuiper Belt Objects
Authors: Matthew S. Tiscareno, Renu Malhotra
(Version v3)

We carried out extensive numerical orbit integrations to probe the long-term chaotic dynamics of the two strongest mean motion resonances of Neptune in the Kuiper belt, the 3:2 (Plutinos) and 2:1 (Twotinos). Our primary results include a computation of the relative volumes of phase space characterized by large- and small-resonance libration amplitudes, and maps of resonance stability measured by mean chaotic diffusion rate. We find that Neptune's 2:1 resonance has weaker overall long-term stability than the 3:2 -- only ~15% of Twotinos are projected to survive for 4 Gyr, compared to ~27% of Plutinos, based on an extrapolation from our 1-Gyr integrations. We find that Pluto has only a modest effect, causing a ~4% decrease in the Plutino population that survives to 4 Gyr. Given current observational estimates, and assuming an initial distribution of particles proportional to the local phase space volume in the resonance, we conclude that the primordial populations of Plutinos and Twotinos formerly made up more than half the population of the classical and resonant Kuiper Belt. We also conclude that Twotinos were originally nearly as numerous as Plutinos; this is consistent with predictions from early models of smooth giant planet migration and resonance sweeping of the Kuiper Belt, and provides a useful constraint for more detailed models.

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Ephemeris Positions Of Distant Minor Planets for 2009 April 29

MPEC 2009 -G25

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