The size, density, and formation of the Orcus-Vanth system in the Kuiper belt - Astrophysics > Earth and Planetary AstrophysicsReportar como inadecuado




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Abstract: The Kuiper belt object Orcus and its satellite Vanth form an unusual systemin the Kuiper belt. Orcus is amongst the largest objects known in the Kuiperbelt, but the relative size of Vanth is much larger than that of the tinysatellites of the other large objects. From Hubble Space Telescope observationswe find that Orcus and Vanth have different visible colors and that Vanth doesnot share the water ice absorption feature seen in the infrared spectrum ofOrcus. We also find that Vanth has a nearly face-on circular orbit with aperiod of 9.5393 +-0.0001 days and semimajor axis of 8980+-20 km, implying asystem mass of 6.32+- 0.01 X 10^20 kg or 3.8% the mass of dwarf planet Eris.From Spitzer Space Telescope observations we find that the thermal emissionis consistent with a single body with diameter 940+-70 km and a geometricalbedo of 0.28+-0.04. Assuming equal densities and albedos, this measurementsimplies sizes of Orcus and Vanth of 900 and 280 km, respectively, and a massratio of 33. Assuming a factor of 2 lower albedo for the non-icy Vanth,however, implies sizes of 820 and 640 km and a mass ratio of 2. The measureddensity depends on the assumed albedo ratio of the two objects but isapproximately 1.5+-0.3 g cm^-3$, midway between typical densities measured forlarger and for smaller objects. The orbit and mass ratio is consistent withformation from a giant impact and subsequent outward tidal evolution and evenconsistent with the system having now achieved a double synchronous state. Thesystem can equally well be explained, however, by initial eccentric capture,Kozai cycling which increases the eccentricity and decreases the pericenter ofthe orbit of Vanth, and subsequent tidal evolution inward.



Autor: M.E. Brown, D. Ragozzine, J. Stansberry, W.C. Fraser

Fuente: https://arxiv.org/







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