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Register a new userThe albedo-color diversity of transneptunian objects
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We analyze albedo data obtained using the Herschel Space Observatory that reveal the existence of two distinct types of surface among midsized transneptunian objects. A color-albedo diagram shows two large clusters of objects, one redder and higher albedo and another darker and more neutrally colored. Crucially, all objects in our sample located in dynamically stable orbits within the classical Kuiper belt region and beyond are confined to the bright-red group, implying a compositional link. Those objects are believed to have formed further from the Sun than the dark-neutral bodies. This color-albedo separation is evidence for a compositional discontinuity in the young solar system.
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We present the results of photometric observations of six Transneptunian objects and three Centaurs, estimations of their rotational periods and corresponding amplitudes. For six of them we present also lower limits of density values. All observations were made using 3.6-m TNG telescope (La Palma, Spain). For four objects -- (148975) 2001 XA255, (281371) 2008 FC76, (315898) 2008 QD4, and 2008 CT190 -- the estimation of short-term variability was made for the first time. We confirm rotation period values for two objects: (55636) 2002 TX300 and (202421) 2005 UQ513, and improve the precision of previously reported rotational period values for other three -- (120178) 2003 OP32, (145452) 2005 RN43, (444030) 2004 NT33 -- by using both our and literature data. We also discuss here that small distant bodies, similarly to asteroids in the Main belt, tend to have double-peaked rotational periods caused by the elongated shape rather than surface albedo variations.
Context. We study the surface properties of transneptunian populations of Solar-system bodies. Aims. We investigate the surface characteristics of the dwarf planet (136472) Makemake and the resonant object (90482) Orcus. Methods. Using the FORS2 instrument of the ESO-VLT we have carried out linear polarisation measurements of Makemake and Orcus. Results. Polarisation of Orcus is similar to that of smaller size objects. The polarimetric properties of Makemake are very close to those of Eris and Pluto. We have not found any significant differences in the polarisation properties of objects from different dynamical classes. However, there are significant differences in polarisation of large and smaller size objects, and between large TNOs with water-ice and methane-ice dominated surfaces. Conclusions. We confirm the different types of polarisation phase behavior for the largest and smaller size TNOs. To explain subtle surface polarisation of Pluto, Makemake and Eris we assume that their surfaces are covered by a thin layer of hoarfrost masking the surface structure.
Physical characterization of Trans-Neptunian objects, a primitive population of the outer solar system, may provide constraints on their formation and evolution. The goal of this work is to characterize a set of 15 scattered disk (SDOs) and detached objects, in terms of their size, albedo, and thermal properties. Thermal flux measurements obtained with the Herschel-PACS instrument at 70, 100 and 160 mu m, and whenever applicable, with Spitzer-MIPS at 24 and 70 mu m, are modeled with radiometric techniques, in order to derive the objects individual size, albedo and when possible beaming factor. Error bars are obtained from a Monte-Carlo approach. We look for correlations between these and other physical and orbital parameters. Diameters obtained for our sample range from 100 to 2400 km, and the geometric albedos (in V band) vary from 3.8 % to 84.5 %. The unweighted mean V geometric albedo for the whole sample is 11.2 % (excluding Eris); 6.9 % for the SDOs, and 17.0 % for the detached objects (excluding Eris). We obtain new bulk densities for three binary systems: Ceto/Phorcys, Typhon/Echidna and Eris/Dysnomia. Apart from correlations clearly due to observational bias, we find significant correlations between albedo and diameter (more reflective objects being bigger), and between albedo, diameter and perihelion distance (brighter and bigger objects having larger perihelia). We discuss possible explanations for these correlations.
The goal of this work is to determine the physical characteristics of resonant, detached and scattered disk objects in the transneptunian region, observed mainly in the framework of the TNOs are Cool! Herschel Open Time Key Program. Based on thermal emission measurements with the Herschel/PACS and Spitzer/MIPS instruments we determine size, albedo, and surface thermal properties for 23 objects using radiometric modelling techniques. This is the first analysis in which the physical properties of objects in the outer resonances are determined for a notable sample. In addition to the results for individual objects, we have compared these characteristics with the bulk properties of other populations of the transneptunian region. The newly analyzed objects show a large variety of beaming factors, indicating a diversity of thermal properties, and in general, they follow the albedo-colour clustering identified earlier for Kuiper belt objects and Centaurs, further strengthening the evidence for a compositional discontinuity in the young Solar System.
We present optical colors of 72 transneptunian objects (TNOs), and infrared colors of 80 TNOs obtained with the WFPC2 and NICMOS instruments, respectively, on the Hubble Space Telescope (HST). Both optical and infrared colors are available for 32 objects that overlap between the datasets. This dataset adds an especially uniform, consistent and large contribution to the overall sample of colors, particularly in the infrared. The range of our measured colors is consistent with other colors reported in the literature at both optical and infrared wavelengths. We find generally good agreement for objects measured by both us and others; 88.1% have better than 2 sigma agreement. The median Hv magnitude of our optical sample is 7.2, modestly smaller (~0.5 mag) than for previous samples. The median absolute magnitude, Hv, in our infrared sample is 6.7. We find no new correlations between color and dynamical properties (semi-major axis, eccentricity, inclination and perihelion). We do find that colors of Classical objects with i<6{deg} come from a different distribution than either the Resonant or excited populations in the visible at the >99.99% level with a K-S test. The same conclusion is found in the infrared at a slightly lower significance level, 99.72%. Two Haumea collision fragments with strong near infrared ice bands are easily identified with broad HST infrared filters and point to an efficient search strategy for identifying more such objects. We find evidence for variability in (19255) 1999 VK8, 1999 OE4, 2000 CE105, 1998 KG62 and 1998 WX31.
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