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Posts: 131433
Date:
Edgeworth-Kuiper debris disk
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Title: An improved model of the Edgeworth-Kuiper debris disk
Authors: Christian Vitense, Alexander V. Krivov, Hiroshi Kobayashi, Torsten Löhne

We access the expected EKB dust disk properties by modelling. We treat the debiased population of the known transneptunian objects (TNOs) as parent bodies and generate the dust with our collisional code. The resulting dust distributions are modified to take into account the influence of gravitational scattering and resonance trapping by planets on migrating dust grains as well as the effect of sublimation. A difficulty is that the amount and distribution of dust are largely determined by sub-kilometre-sized bodies. These are directly unobservable, and their properties cannot be accessed by collisional modelling, because objects larger than 10...60m in the present-day EKB are not in a collisional equilibrium. To place additional constraints, we use in-situ measurements of the New Horizons spacecraft within 20AU. We show that the TNO population has to have a break in the size distribution at s10AU)~10^-6 and their fractional luminosity is f_d~10^-7. Planets and sublimation are found to have little effect on dust impact fluxes and dust thermal emission. The spectral energy distribution of an EKB analogue, as would be seen from 10pc distance, peaks at wavelengths of 40...50\mum at F~0.5mJy, which is less than 1% of the photospheric flux at those wavelengths. Therefore, exact EKB analogues cannot be detected with present-day instruments such as Herschel/PACS.

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Posts: 131433
Date:
RE: Kuiper Belt
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Title: SDSS Observations of Kuiper Belt Objects: Colours and Variability
Authors: Eran O. Ofek

Colours of Trans Neptunian Objects (TNOs) are used to study the evolutionary processes of bodies in the outskirts of the Solar System, and to test theories regarding their origin. Here I describe a search for serendipitous Sloan Digital Sky Survey (SDSS) observations of known TNOs and Centaurs. I present a catalogue of SDSS photometry, colours and astrometry of 388 measurements of 42 outer Solar-System objects. I find a weak evidence, at the ~2-sigma level (per trial), for a correlation between the g-r colour and inclination of scattered disk objects and hot classical KBOs. I find a correlation between the g-r colour and the angular momentum in the z direction of all the objects in this sample. Light curves as a function of phase angle are constructed for 13 objects. The steepness of the slopes of these light curves suggests that the coherent backscatter mechanism plays a major role in the reflectivity of outer Solar-System small objects at small phase angles. I find a weak evidence for an anti-correlation, significant at the 2-sigma confidence level (per trial), between the g-band phase angle slope parameter and the semi-major axis, as well as the aphelion distance, of these objects. I discuss the origin of this possible correlation and argue that if this correlation is real it probably indicates that "Sedna"-like objects have a different origin than other classes of TNOs. Finally, I identify several objects with large variability amplitudes.

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Title: The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: The Compositional Classes of the Kuiper Belt
Authors: W. C. Fraser, M. E. Brown

We present the first results of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was to measure the surface properties of a large number of Kuiper belt objects and attempt to infer compositional and dynamical correlations. We find that the Centaurs and the low-perihelion scattered disk and resonant objects exhibit virtually identical bifurcated optical colour distributions and make up two well defined groups of object. Both groups have highly correlated optical and NIR colours which are well described by a pair of two component mixture models that have different red components, but share a common neutral component. The small, H_{606}\gtrsim5.6 high-perihelion excited objects are entirely consistent with being drawn from the two branches of the mixing model suggesting that the colour bifurcation of the Centaurs is apparent in all small excited objects. On the other hand, objects larger than H_{606}~5.6 are not consistent with the mixing model, suggesting some evolutionary process avoided by the smaller objects. The existence of a bifurcation amongst all excited populations argues that the two separate classes of object existed in the primordial disk before the excited Kuiper belt was populated. The cold classical objects exhibit a different type of surface which has colours that are consistent with being drawn from the red branch of the mixing model, but with much higher albedos.

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Title: Neptune on tiptoes: dynamical histories that preserve the cold classical Kuiper belt
Authors: Schuyler Wolff, Rebekah I. Dawson, Ruth A. Murray-Clay

The current dynamical structure of the Kuiper belt was shaped by the orbital evolution of the giant planets, especially Neptune, during the era following planet formation, when the giant planets may have undergone planet-planet scattering and/or planetesimal-driven migration. Numerical simulations of this process, while reproducing many properties of the belt, fail to generate the high inclinations and eccentricities observed for some objects while maintaining the observed dynamically "cold" population. We present the first of a three-part parameter study of how different dynamical histories of Neptune sculpt the planetesimal disk. Here we identify which dynamical histories allow an in situ planetesimal disk to remain dynamically cold, becoming today's cold Kuiper belt population. We find that if Neptune undergoes a period of elevated eccentricity and/or inclination, it secularly excites the eccentricities and inclinations of the planetesimal disk. We demonstrate that there are several well-defined regimes for this secular excitation, depending on the relative timescales of Neptune's migration, the damping of Neptune's orbital inclination and/or eccentricity, and the secular evolution of the planetesimals. We model this secular excitation analytically in each regime, allowing for a thorough exploration of parameter space. Neptune's eccentricity and inclination can remain high for a limited amount of time without disrupting the cold classical belt. In the regime of slow damping and slow migration, if Neptune is located (for example) at 20 AU, then its eccentricity must stay below 0.18 and its inclination below 6°.

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Title: A hypothesis for the colour diversity of the Kuiper belt
Authors: M.E. Brown, E.L. Schaller, W.C. Fraser

We propose a chemical and dynamical process to explain the surface colors of the Kuiper belt. In our hypothesis, the initial bulk compositions of the bodies themselves can be quite diverse -- as is seen in comets -- but the early surface compositions are set by volatile evaporation after the objects are formed. Strong gradients in surface composition, coupled with UV and particle irradiation, lead to the surface colours that are seen today. The objects formed in the inner part of the primordial belt retain only H2O and CO2 as the major ice species on their surfaces. Irradiation of these species plausibly results in the dark neutrally coloured centaurs and KBOs. Object formed further in the disk retain CH3OH, which has been shown to lead to brighter redder surfaces after irradiation, as seen in the brighter redder centaurs and KBOs. Objects formed at the current location of the cold classical Kuiper belt uniquely retain NH3, which has been shown to affect irradiation chemistry and could plausibly lead to the unique colours of these objects. We propose observational and experimental tests of this hypothesis.

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Posts: 131433
Date:
Bright Kuiper Belt Objects
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Title: A Southern Sky and Galactic Plane Survey for Bright Kuiper Belt Objects
Authors: Scott Sheppard (Carnegie Institution of Washington), Andrzej Udalski (Warsaw University), Chad Trujillo (Gemini), Marcin Kubiak, Grzegorz Pietrzynski, Radoslaw Poleski, Igor Soszynski, Michal Szyma, Krzysztof Ulaczyk

About 2500 square degrees of sky south of declination -25 degrees and/or near the galactic plane were surveyed for bright outer solar system objects. This survey is one of the first large scale southern sky and galactic plane surveys to detect dwarf planets and other bright Kuiper Belt objects in the trans-Neptunian region. The survey was able to obtain a limiting R-band magnitude of 21.6. In all, 18 outer solar system objects were detected, including Pluto which was detected near the galactic center using optimal image subtraction techniques to remove the high stellar density background. Fourteen of the detections were previously unknown trans-Neptunian objects, demonstrating that the southern sky had not been well-searched to date for bright outer solar system objects. Assuming moderate albedos, several of the new discoveries from this survey could be in hydrostatic equilibrium and thus be considered dwarf planets. Combining this survey with previous surveys from the northern hemisphere suggests that the Kuiper Belt is nearly complete to around 21st magnitude in the R-band. All the main dynamical classes in the Kuiper Belt are occupied by at least one dwarf planet sized object. The 3:2 Neptune resonance, which is the innermost well-populated Neptune resonance, has several large objects while the main outer Neptune resonances such as the 5:3, 7:4, 2:1, and 5:2 do not appear have any large objects. This indicates that the outer resonances are either significantly depleted in objects relative to the 3:2 resonance or have a significantly different assortment of objects than the 3:2 resonance. For the largest objects (H<4.5 mag), the scattered disk population appears to have a few times more objects than the main Kuiper Belt population, while the Sedna population could be several times more than that of the main Kuiper Belt.

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Posts: 131433
Date:
Twelve Plutinos
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Orbital elements:
2004 HX78
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 357.95644              (2000.0)            P               Q
n   0.00398889     Peri.   19.76394     -0.37263066     +0.90350174
a  39.3763012      Node   228.98963     -0.88468443     -0.41475455
e   0.1518590      Incl.   16.29563     -0.28014255     +0.10799660
P 247              H    7.8           G   0.15           U   4


2004 HY78
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 359.60699              (2000.0)            P               Q
n   0.00401802     Peri.  194.20709     -0.77505378     +0.62502021
a  39.1857550      Node    25.21094     -0.55636053     -0.60523407
e   0.1934100      Incl.   12.60557     -0.29959071     -0.49299235
P 245              H    8.3           G   0.15           U   3


2004 HZ78
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 337.58993              (2000.0)            P               Q
n   0.00397504     Peri.  221.43805     -0.39495644     +0.91320689
a  39.4676659      Node    25.78180     -0.77046130     -0.26977354
e   0.1492076      Incl.   13.33431     -0.50039863     -0.30541025
P 248              H    7.3           G   0.15           U   3


2004 HA79
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M  80.74082              (2000.0)            P               Q
n   0.00400617     Peri.  262.12200     -0.23509069     -0.95988303
a  39.2629615      Node   203.27755     +0.97196575     -0.23153924
e   0.2468517      Incl.   22.75113     +0.00386542     -0.15815864
P 246              H    7.2           G   0.15           U   4


2004 HB79
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 341.56562              (2000.0)            P               Q
n   0.00402271     Peri.  189.31937     -0.31059743     +0.94964572
a  39.1552578      Node    62.59476     -0.86908386     -0.26613249
e   0.2271377      Incl.    2.66372     -0.38499672     -0.16536782
P 245              H    8.7           G   0.15           U   4


2004 KB19
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 292.13173              (2000.0)            P               Q
n   0.00397793     Peri.  286.70231     +0.84239363     +0.49823828
a  39.4485928      Node    44.00153     -0.30814758     +0.75789026
e   0.2201757      Incl.   17.18602     -0.44206112     +0.42114246
P 248              H    7.4           G   0.15           U   4


2004 KC19
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 359.69898              (2000.0)            P               Q
n   0.00401365     Peri.    7.18886     -0.37828856     +0.92171370
a  39.2141734      Node   240.61614     -0.85412169     -0.38323094
e   0.2352358      Incl.    5.64323     -0.35689481     -0.05981563
P 246              H    8.3           G   0.15           U   3


2004 MS8
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M  15.13254              (2000.0)            P               Q
n   0.00396734     Peri.  345.58984     +0.07381259     +0.97673665
a  39.5187208      Node   288.33442     -0.89270006     -0.02528629
e   0.2991222      Incl.   12.24578     -0.44456530     +0.21294630
P 248              H    8.3           G   0.15           U   4


2004 VX130
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M  53.05035              (2000.0)            P               Q
n   0.00394076     Peri.  292.43998     +0.91625775     +0.39443806
a  39.6962537      Node    44.41243     -0.32089210     +0.82719554
e   0.2110925      Incl.    5.73499     -0.23979157     +0.40020764
P 250              H    7.7           G   0.15           U   3


2004 VY130
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M   8.59938              (2000.0)            P               Q
n   0.00395448     Peri.  180.67450     +0.73131714     -0.67155130
a  39.6043640      Node   222.33908     +0.62658262     +0.73052011
e   0.2810464      Incl.   10.18871     +0.26938718     +0.12393230
P 249              H    8.1           G   0.15           U   2


2004 VZ130
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M  23.95773              (2000.0)            P               Q
n   0.00392230     Peri.  334.89556     +0.96069067     -0.24584882
a  39.8207085      Node    40.03659     +0.27629698     +0.80137262
e   0.2862568      Incl.   11.56505     +0.02708165     +0.54530751
P 251              H    8.9           G   0.15           U   2


2005 CD81
Epoch 2011 Feb. 8.0 TT = JDT 2455600.5                  MPC
M 183.21482              (2000.0)            P               Q
n   0.00401599     Peri.    2.79877     +0.77131258     +0.58762824
a  39.1989527      Node   317.87640     -0.59078861     +0.51815869
e   0.1532474      Incl.   21.37655     -0.23673979     +0.62145364
P 245              H    7.1           G   0.15           U   5

MPEC 2011 - G81



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L

Posts: 131433
Date:
RE: Kuiper Belt
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Title: Observed Binary Fraction Sets Limits on the Extent of Collisional Grinding in the Kuiper Belt
Authors: David Nesvorny, David Vokrouhlicky, William F. Bottke, Keith Noll, Harold F. Levison

The size distribution in the cold classical Kuiper belt can be approximated by two idealized power laws: one with steep slope for radii R>R* and one with shallow slope for R<R*, where R*~25-50 km. Previous works suggested that the SFD roll-over at R* can be the result of extensive collisional grinding in the Kuiper belt that led to the catastrophic disruption of most bodies with R<R*. Here we use a new code to test the effect of collisions in the Kuiper belt. We find that the observed roll-over could indeed be explained by collisional grinding provided that the initial mass in large bodies was much larger than the one in the present Kuiper belt, and was dynamically depleted. In addition to the size distribution changes, our code also tracks the effects of collisions on binary systems. We find that it is generally easier to dissolve wide binary systems, such as the ones existing in the cold Kuiper belt today, than to catastrophically disrupt objects with R~R*. Thus, the binary survival sets important limits on the extent of collisional grinding in the Kuiper belt. We find that the extensive collisional grinding required to produce the SFD roll-over at R* would imply a strong gradient of the binary fraction with R and separation, because it is generally easier to dissolve binaries with small components and/or those with wide orbits. The expected binary fraction for R<R* is <0.1. The present observational data do not show such a gradient. Instead, they suggest a large binary fraction of ~0.4 for R=30-40 km. This may indicate that the roll-over was not produced by disruptive collisions, but is instead a fossil remnant of the KBO formation process.

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Posts: 131433
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Haleakala's new Pan-STARRS-1 telescope might help scientists identify a host of new objects

In the outer reaches of the solar system, in a mysterious and remote area known as the Kuiper Belt, spins one dwarf planet named after the Hawaiian goddess of fertility and childbirth and another bearing the name of Rapa Nui's birdlike god of creation.
Haumea and Makemake - and the former, demoted planet Pluto - are among five larger identified objects in the Kuiper Belt, a collection of oddball rocks and ice beyond the orbit of Neptune.
And as a new telescope atop Haleakala is quickly enumerating, the largely unexplored region is proving to be home to thousands of smaller objects that could one day carry the names of other Polynesian deities.

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Posts: 131433
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Kuiper Belt may be born of collisions

The cold and shadowy fringe of the solar system known as the Kuiper belt is generating increasing debate among scientists as data accumulates on the growing population of objects discovered there. Now, two new studies of Kuiper belt objects presented 5 October at a meeting of the American Astronomical Society's Division for Planetary Sciences in Pasadena, California, may reveal a crucial hole a prevailing model of the solar system's early history.
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