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We measured the system-integrated thermal emission of the binary Kuiper Belt object (47171 ) 1999 TC36, at wavelengths near 24 and 70 μm using the Spitzer Space Telescope. We fit these data and the visual magnitude using both the standard thermal model and thermophysical models. We find that the effective diameter of the binary is 405 km, with a range of 350-470 km, and the effective visible geometric albedo for the system is 0.079, with a range of 0.055-0.11. The binary orbit, magnitude contrast between the components, and system mass have been determined from HSTdata studied by Margot et al. Our effective diameter, combined with that system mass, indicates an average density for the objects of 0.5 g cm-3, with a range 0.3-0.8 g cm -3. This density is low compared to that of materials expected to be abundant in solid bodies in the trans-Neptunian region, requiring 50%-75% of the interior of (47171 ) 1999 TC36 be taken up by void space. This conclusion is not greatly affected if (47171)1999 TC36 is "differentiated" (in the sense of having either a rocky or just a nonporous core). If the primary is itself a binary, the average density of that (hypothetical) triple system would be in the range 0.4-1.l g cm -3, with a porosity in the range 15%-70%. © 2006. The American Astronomical Society. All rights reserved.

The abundances of main carbon- and oxygen-bearing gases in the atmospheres of giant exoplanets provide insights into atmospheric chemistry and planet formation processes 1,2 . Thermochemistry suggests that methane (CH 4 ) should be the dominant carbon-bearing species below about 1,000 K over a range of plausible atmospheric compositions 3 ; this is the case for the solar system planets 4 and has been confirmed in the atmospheres of brown dwarfs and self-luminous, directly imaged exoplanets 5 . However, CH 4 has not yet been definitively detected with space-based spectroscopy in the atmosphere of a transiting exoplanet 6-11 , but a few detections have been made with ground-based, high-resolution transit spectroscopy 12,13 including a tentative detection for WASP-80b (ref. 14 ). Here we report transmission and emission spectra spanning 2.4-4.0 μm of the 825 K warm Jupiter WASP-80b taken with the NIRCam instrument of the JWST, both of which show strong evidence of CH 4 at greater than 6σ significance. The derived CH 4 abundances from both viewing geometries are consistent with each other and with solar to sub-solar C/O and around five times solar metallicity, which is consistent with theoretical predictions 15-17 ., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU 69 ). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU 69 , a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU 69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU 69 's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on Pluto's surface have been attributed to tholin-like organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location on Charon implicates the temperature extremes that result from Charon's high obliquity and long seasons in the production of this material. The escape of Pluto's atmosphere provides a potential feedstock for a complex chemistry. Gas from Pluto that is transiently cold-trapped and processed at Charon's winter pole was proposed as an explanation for the dark coloration on the basis of an image of Charon's northern hemisphere, but not modelled quantitatively. Here we report images of the southern hemisphere illuminated by Pluto-shine and also images taken during the approach phase that show the northern polar cap over a range of longitudes. We model the surface thermal environment on Charon and the supply and temporary cold-trapping of material escaping from Pluto, as well as the photolytic processing of this material into more complex and less volatile molecules while cold-trapped. The model results are consistent with the proposed mechanism for producing the observed colour pattern on Charon.

The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile methane, carbon monoxide, and nitrogen ices that dominate Pluto's surface have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological time scales. Pluto's water ice "bedrock" was also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's color pattern is simpler, dominated by neutral low latitudes and a reddish northern polar region. Charon's near-infrared spectra reveal highly localized areas with strong ammonia absorption tied to small craters with relatively fresh-appearing impact ejecta., (Copyright © 2016, American Association for the Advancement of Science.)

A stellar-occultation light curve for Triton shows asymmetry that can be understood if Triton's middle atmosphere is distorted from spherical symmetry. Although a globally oblate model can explain the data, the inferred atmospheric flattening is so large that it could be caused only by an unrealistic internal mass distribution or highly supersonic zonal winds. Cyclostrophic winds confined to a jet near Triton's northern or southern limbs (or both) could also be responsible for the details of the light curve, but such winds are required to be slightly supersonic. Hazes and clouds in the atmosphere are unlikely to have caused the asymmetry in the light curve.