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TOPIC: Trans-Neptunian objects
Blobrana


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Title: TNOs are Cool: a survey of the Transneptunian Region XII. Thermal light curves of Haumea, 2003 VS2 and 2003 AZ84 with Herschel Space Observatory-PACS
Author: P. Santos-Sanz (1), E. Lellouch (2), O. Groussin (3), P. Lacerda (4), T.G. Mueller (5), J.L. Ortiz (1), C. Kiss (6), E. Vilenius (5,7), J. Stansberry (8), R. Duffard (1), S. Fornasier (2,9), L. Jorda (3), A. Thirouin (10) ( (1) Instituto de Astrofisica de Andalucia (CSIC), Spain, (2) LESIA-Observatoire de Paris, CNRS, UPMC Univ. Paris 6, Univ. Paris-Diderot, France, (3) Aix Marseille Universite, CNRS, LAM, France, (4) Astrophysics Research Centre, Queen's University Belfast, United Kingdom, (5) Max-Planck-Institut fur extraterrestrische Physik (MPE), Germany, (6) Konkoly Observatory of the Hungarian Academy of Sciences, Hungary, (7) Max-Planck-Institut fur Sonnensystemforschung (MPS), Germany, (8) Space Telescope Science Institute, USA, (9) Univ.Paris Diderot, France, (10) Lowell Observatory, USA)

Time series observations of the dwarf planet Haumea and the Plutinos 2003VS2 and 2003AZ84 with Herschel/PACS are presented in this work. Thermal emission of these trans-Neptunian objects were acquired as part of the TNOs are Cool Herschel Space Observatory key programme. We search for the thermal light curves at 100 and 160um of Haumea and 2003AZ84, and at 70 and 160um for 2003VS2 by means of photometric analysis of the PACS data. The goal of this work is to use these thermal light curves to obtain physical and thermophysical properties of these icy Solar System bodies. Haumea's thermal light curve is clearly detected at 100 and 160um. The effect of the reported dark spot is apparent at 100um. Different thermophysical models were applied to these light curves, varying the thermophysical properties of the surface within and outside the spot. Although no model gives a perfect fit to the thermal observations, results imply an extremely low thermal inertia (< 0.5 MKS) and a high phase integral (> 0.73) for Haumea's surface. We note that the dark spot region appears to be only weakly different from the rest of the object, with modest changes in thermal inertia and/or phase integral. The thermal light curve of 2003VS2 is not firmly detected at 70 and at 160um but a thermal inertia of 2+/-0.5 MKS can be derived from these data. The thermal light curve of 2003AZ84 is not firmly detected at 100um. We apply a thermophysical model to the mean thermal fluxes and to all the Herschel/PACS and Spitzer/MIPS thermal data of 2003AZ84, obtaining a close to pole-on orientation as the most likely for this TNO. For the three TNOs, the thermal inertias derived from light curve analyses or from the thermophysical analysis of the mean thermal fluxes confirm the generally small or very small surface thermal inertias of the TNO population, which is consistent with a statistical mean value of 2.5+/-0.5 MKS.

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Blobrana


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Title: Study and application of the resonant secular dynamics beyond Neptune
Author: Melaine Saillenfest, Marc Fouchard, Giacomo Tommei, Giovanni B. Valsecchi

We use a secular representation to describe the long-term dynamics of transneptunian objects in mean-motion resonance with Neptune. The model applied is thoroughly described in Saillenfest et al. (2016). The parameter space is systematically explored, showing that the secular trajectories depend little on the resonance order. High-amplitude oscillations of the perihelion distance are reported and localised in the space of the orbital parameters. In particular, we show that a large perihelion distance is not a sufficient criterion to declare that an object is detached from the planets. Such a mechanism, though, is found unable to explain the orbits of Sedna or 2012VP113, which are insufficiently inclined (considering their high perihelion distance) to be possibly driven by such a resonant dynamics. The secular representation highlights the existence of a high-perihelion accumulation zone due to resonances of type 1:k with Neptune. That region is found to be located roughly at semi-major axes in [100;300] AU, perihelion distances in [50;70] AU and inclinations [30;50]{\deg}. In addition to the flux of objects directly coming from the Scattered Disc, numerical simulations show that the Oort Cloud is also a substantial source for such objects. Naturally, as that mechanism relies on fragile captures in high-order resonances, our conclusions break down in the case of a significant external perturber. The detection of such a reservoir could thus be an observational constraint to probe the external Solar System.

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Blobrana


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Title: A FIR-Survey of TNOs and Related Bodies
Author: J. M. Bauer, P. F. Goldsmith, C. M. Bradford, A. J. Lovell

The small solar-system bodies that reside between 30 and 50 AU are often referred to as the Trans Neptunian Objects, or TNOs. A far-infrared (FIR) mission with survey capabilities, like the prospective Cryogenic Aperture Large Infrared Space Telescope Observatory (CALISTO; Goldsmith et al. 2008), offers the potential for the first time of really probing the population of TNOs, and related populations, down to moderates sizes, and out to distances exceeding 100 AU from the Sun.

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Blobrana


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Title: "TNOs Are Cool": A survey of the transneptunian region. XII. The albedo-color diversity of transneptunian objects
Author: Pedro Lacerda, Sonia Fornasier, Emmanuel Lellouch, Csaba Kiss, Esa Vilenius, Pablo Santos-Sanz, Miriam Rengel, Thomas Mueller, John Stansberry, Rene Duffard, Audrey Delsanti, Aurelie Guilbert-Lepoutre

We analyse albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized transneptunian objects. A colour-albedo diagram shows two large clusters of objects, one redder and higher albedo and another darker and more neutrally coloured. Crucially, all objects located in dynamically stable orbits within the classical Kuiper belt region and beyond are confined to the brighter and redder of the two groups, implying a compositional link. Those objects are believed to have formed further from the Sun than the dark-neutral bodies. This colour-albedo separation is evidence for a compositional discontinuity in the young solar system.

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Blobrana


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Title: Extreme trans-Neptunian objects and the Kozai mechanism: signaling the presence of trans-Plutonian planets?
Author: C. de la Fuente Marcos, R. de la Fuente Marcos

The existence of an outer planet beyond Pluto has been a matter of debate for decades and the recent discovery of 2012 VP113 has just revived the interest for this controversial topic. This Sedna-like object has the most distant perihelion of any known minor planet and the value of its argument of perihelion is close to 0 degrees. This property appears to be shared by almost all known asteroids with semimajor axis greater than 150 au and perihelion greater than 30 au (the extreme trans-Neptunian objects or ETNOs), and this fact has been interpreted as evidence for the existence of a super-Earth at 250 au. In this scenario, a population of stable asteroids may be shepherded by a distant, undiscovered planet larger than the Earth that keeps the value of their argument of perihelion librating around 0 degrees as a result of the Kozai mechanism. Here, we study the visibility of these ETNOs and confirm that the observed excess of objects reaching perihelion near the ascending node cannot be explained in terms of any observational biases. This excess must be a true feature of this population and its possible origin is explored in the framework of the Kozai effect. The analysis of several possible scenarios strongly suggest that at least two trans-Plutonian planets must exist.

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Blobrana


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Title: Dynamical formation of detached trans-Neptunian objects close to the 2:5 and 1:3 mean motion resonances with Neptune
Author: P. I. O. Brasil, R. S. Gomes, J. S. Soares

Through a semi-analytic approach of the Kozai resonance inside an MMR, we show phase diagrams (e,{\omega}) that suggest the possibility of a scattered particle, after being captured in an MMR with Neptune, to become a detached object. We ran several numerical integrations with thousands of particles perturbed by the four major planets, and there are cases with and without Neptune's residual migration. These were developed to check the semi-analytic approach and to better understand the dynamical mechanisms that produce the detached objects close to an MMR. The numerical simulations with and without a residual migration for Neptune stress the importance of a particular resonance mode, which we name the hibernating mode, on the formation of fossilized detached objects close to MMRs. When considering Neptune's residual migration we are able to show the formation of detached orbits. These objects are fossilized and cannot be trapped in the MMRs again. We find a ratio of the number of fossilised objects with moderate perihelion distance (35 < q < 40 au) to the number of objects with high perihelion distance (q > 40 au) as 3.0/1 for objects close to the 2:5, and 1.7/1 for objects close to the 1:3 resonance. We estimate that the two fossilised population have a total mass between 0.1 and 0.3 Pluto's mass.

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Title: "TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations
Author: E. Vilenius (1), C. Kiss (2), T. Müller (1), M. Mommert (3 and 4), P. Santos-Sanz (5 and 6), A. Pįl (2), J. Stansberry (7), M. Mueller (8 and 9), N. Peixinho (10 and 11), E. Lellouch (6), S. Fornasier (6 and 12), A. Delsanti (6 and 13), A. Thirouin (5), J. L. Ortiz (5), R. Duffard (5), D. Perna (6), F. Henry (6) ((1) Max-Planck-Institut für extraterrestrische Physik, Germany, (2) Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungary, (3) Deutsches Zentrum für Luft- und Raumfahrt e.V., Institute of Planetary Research, Germany, (4) Northern Arizona University, Department of Physics and Astronomy, USA, (5) Instituto de Astrofķsica de Andalucķa (CSIC), Spain, (6) LESIA-Observatoire de Paris, CNRS, UPMC Univ., France, (7) Stewart Observatory, The University of Arizona, USA, (8) SRON Netherlands Institute for Space Research, Netherlands, (9) UNS-CNRS-Observatoire de la Cōte d'Azur, France, (10) Geophysical and Astronomical Observatory of the University of Coimbra, Portugal, (11) Unidad de Astronomķa, Facultad de Ciencias Bįsicas, Universidad de Antofagasta, Chile, (12) Univ. Paris Diderot, France, (13) Laboratoire d'Astrophysique de Marseille, CNRS, Université de Provence, France)

The classical Kuiper belt contains objects both from a low-inclination, presumably primordial, distribution and from a high-inclination dynamically excited population. Based on a sample of classical TNOs with observations at thermal wavelengths we determine radiometric sizes, geometric albedos and thermal beaming factors as well as study sample properties of dynamically hot and cold classicals. Observations near the thermal peak of TNOs using infra-red space telescopes are combined with optical magnitudes using the radiometric technique with near-Earth asteroid thermal model (NEATM). We have determined three-band flux densities from Herschel/PACS observations at 70.0, 100.0 and 160.0 m and Spitzer/MIPS at 23.68 and 71.42 m when available. We have analysed 18 classical TNOs with previously unpublished data and re-analysed previously published targets with updated data reduction to determine their sizes and geometric albedos as well as beaming factors when data quality allows. We have combined these samples with classical TNOs with radiometric results in the literature for the analysis of sample properties of a total of 44 objects. We find a median geometric albedo for cold classical TNOs of 0.14 and for dynamically hot classical TNOs, excluding the Haumea family and dwarf planets, 0.085. We have determined the bulk densities of Borasisi-Pabu (2.1 g/cm^3), Varda-Ilmare (1.25 g/cm^3) and 2001 QC298 (1.14 g/cm^3) as well as updated previous density estimates of four targets. We have determined the slope parameter of the debiased cumulative size distribution of dynamically hot classical TNOs as q=2.3 +- 0.1 in the diameter range 100<D<500 km. For dynamically cold classical TNOs we determine q=5.1 +- 1.1 in the diameter range 160<D<280 km as the cold classical TNOs have a smaller maximum size.

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Blobrana


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Title: TNOs are Cool: A survey of the trans-Neptunian region. VIII. Combined Herschel PACS and SPIRE observations of 9 bright targets at 70--500 micron
Authors: S. Fornasier, E. Lellouch, T. Müller, P. Santos-Sanz, P. Panuzzo, C. Kiss, T. Lim, M. Mommert, D. Bockelée-Morvan, E. Vilenius, J. Stansberry, G.P. Tozzi, S. Mottola, A. Delsanti, J. Crovisier, R. Duffard, F. Henry, P. Lacerda, A. Barucci, A. Gicquel

Transneptunian objects (TNOs) are bodies populating the Kuiper Belt and they are believed to retain the most pristine and least altered material of the solar system. The Herschel Open Time Key Program entitled "TNOs are Cool: A survey of the trans-Neptunian region" has been awarded 373 h to investigate the albedo, size distribution and thermal properties of TNOs and Centaurs. Here we focus on the brightest targets observed by both the PACS and SPIRE multiband photometers: the dwarf planet Haumea, six TNOs (Huya, Orcus, Quaoar, Salacia, 2002 UX25, and 2002 TC302), and two Centaurs (Chiron and Chariklo). Flux densities are derived from PACS and SPIRE instruments using optimised data reduction methods. The spectral energy distribution obtained with the Herschel PACS and SPIRE instruments over 6 bands (centred at 70, 100, 160, 250, 350, and 500 µm), and with Spitzer-MIPS at 23.7 and 71.4 µm has been modelled with the NEATM thermal model in order to derive the albedo, diameter, and beaming factor. For the Centaurs Chiron and Chariklo and for the 1000 km sized Orcus and Quaoar, a thermophysical model was also run to better constrain their thermal properties. We derive the size, albedo, and thermal properties, including thermal inertia and surface emissivity, for the 9 TNOs and Centaurs. Several targets show a significant decrease in their spectral emissivity longwards of ~300 µm and especially at 500 µm. Using our size estimations and the mass values available in the literature, we also derive the bulk densities for the binaries Quaoar/Weywot (2.18^{+0.43}_{-0.36} g/cm³), Orcus/Vanth (1.53^{+0.15}_{-0.13} g/cm³), and Salacia/Actea (1.29^{+0.29}_{-0.23} g/cm³). Quaoar's density is similar to that of the other dwarf planets Pluto and Haumea, and its value implies high contents of refractory materials mixed with ices.

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Blobrana


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Transneptunian Objects
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Title: Lightcurves of 32 Large Transneptunian Objects
Authors: Susan D. Benecchi, Scott S. Sheppard

We present observations of 32 primarily bright, newly discovered Transneptunian objects observable from the Southern Hemisphere during 39 nights of observation with the 2.5-m telescope at Las Campanas Observatory. Our dataset includes objects in all dynamical classes, but is weighted towards Scattered objects. We find 15 objects for which we can fit periods and amplitudes to the data, and place lightcurve amplitude upper limits on the other 17 objects. Combining our sample with the larger sample in the literature, we find a 3-sigma correlation between lightcurve amplitude and absolute magnitude with fainter objects having larger lightcurve amplitudes. We looked for correlations between lightcurve and individual orbital properties, but did not find any statistically significant results. However, if we consider lightcurve properties with respect to dynamical classification, we find statistically different distributions between the Classical-Scattered and Classical-Resonant populations, respectively, with the Classical objects having larger amplitude lightcurves. The properties of binary lightcurves are largely consistent with the greater population except in the case of tidally locked systems. All the Haumea family objects measured so far have lightcurve amplitudes le 0.3 magnitudes and rotation periods le 10 hours suggesting that they are not significantly different from the larger population, although no large amplitudes have yet been measured among this group. We expect multiple factors are influencing object rotations: object size dominates lightcurve properties except in the case of tidal, or proportionally large collisional interactions with other objects, the influence of the latter being different for each sub-population. We also present phase curves and colours for some objects; our values are not significantly different from those presented in the literature for other samples.

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Blobrana


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Title: Trans-Neptunian objects as natural probes to the unknown solar system
Authors: Patryk Sofia Lykawka

Trans-Neptunian objects (TNOs) are icy/rocky bodies that move beyond the orbit of Neptune in a region known as the trans-Neptunian belt (or Edgeworth-Kuiper belt). In contrast to the predictions of accretion models that feature protoplanetary disk planetesimals evolving on dynamically cold orbits (with both very small eccentricities, e, and inclinations, i), in reality TNOs exhibit surprisingly wide ranges of orbital eccentricities and inclinations. Several theoretical models have addressed the origin and orbital evolution of the main dynamical classes of TNOs, but none have successfully reproduced them all. In addition, none have explained several objects on peculiar orbits, or provided insightful predictions, without which a model cannot be tested properly against observations. Based on extensive simulations of planetesimal disks with the presence of the four giant planets and huge numbers of modelled planetesimals, I explore in detail the dynamics of the TNOs, in particular their (un)stable regions over timescales comparable to the age of the solar system, and the role of resonances across the entire trans-Neptunian region. I also propose that, along with the orbital history of the giant planets, the orbital evolution of primordial embryos (massive planetesimals comparable to Mars-Earth masses) can explain the fine orbital structure of the trans-Neptunian belt, the orbits of Jovian and Neptunian Trojans, and possibly the current orbits of the giant planets. Those primordial embryos were ultimately scattered by the giant planets, a process that stirred both the orbits of the giant planets and the primordial planetesimal disk to the levels observed at 40-50 AU. In particular, the main constraints provided by the trans-Neptunian belt are optimally satisfied if at least one such primordial embryo (planetoid) survived in the outskirts of the solar system.

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