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Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report(More)
Context. The large number and all-sky distribution of quasars from different surveys, along with their presence in large, deep astro-metric catalogs, enables the building of an optical materialization of the ICRS following its defining principles. Namely, kinematically non-rotating with respect to the ensemble of distant extragalactic objects; aligned with(More)
Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by(More)
The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1 AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great(More)
Context. The potentially hazardous asteroid (99942) Apophis, previously designated 2004 MN4, is emblematic of the study of asteroids that could impact the Earth in the near future. Orbit monitoring and error propagation analysis are mandatory to predict the probability of an impact and, furthermore, its possible mitigation. Several aspects for this(More)
We report the observation of a multi-chord stellar occultation by the dwarf planet (136199) Eris. The event was observed on November 6, 2010 UT, from two sites in Chile. Our observation is consistent with a spherical Eris with radius RE=1163±6 km, density ρ=2.52±0.05 g cm−3, and visible geometric albedo pV=0.96 −0.04. Besides being remarkably similar in(More)
Context. Investigation of transneptunian objects, including Pluto and its satellites, by stellar occultations. Aims. Derive precise, astrometric predictions for stellar occultations by Pluto and its satellites Charon, Hydra and Nix for 2008–2015. Construct an astrometric star catalog in the UCAC2 system covering Plutos sky path. Methods. We have carried out(More)
We collected mid-IR spectra from 5.2 to 38 μm using the Spitzer Space Telescope Infrared Spectrograph of 28 asteroids representative of all established types of binary groups. Photometric lightcurves were also obtained for 14 of them during the Spitzer observations to provide the context of the observations and reliable estimates of their absolute(More)
Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf(More)
Haumea-one of the four known trans-Neptunian dwarf planets-is a very elongated and rapidly rotating body. In contrast to other dwarf planets, its size, shape, albedo and density are not well constrained. The Centaur Chariklo was the first body other than a giant planet known to have a ring system, and the Centaur Chiron was later found to possess something(More)