Abstract
The recent discovery1,2 of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth3,4,5, main-belt6,7,8,9,10 and Trojan11 asteroids have subsequently been discovered. The Kuiper belt—the region of space extending from Neptune (at 30 astronomical units) to well over 100 AU and believed to be the source of new short-period comets12—has become a fascinating new window onto the formation of our Solar System since the first member object, not counting Pluto, was discovered in 1992 (ref. 13). Here we report that the Kuiper-belt object 1998 WW31 is binary with a highly eccentric orbit (eccentricity e ≈ 0.8) and a long period (about 570 days), very different from the Pluto/Charon system, which was hitherto the only previously known binary in the Kuiper belt. Assuming a density in the range of 1 to 2 g cm-3, the albedo of the binary components is between 0.05 and 0.08, close to the value of 0.04 generally assumed for Kuiper-belt objects.
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Acknowledgements
C.V., A.D., D.J.T. and M.C. are visiting astronomers at the Canada-France-Hawaii Telescope (CFHT), operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France and the University of Hawaii. J.Wm.P. and M.B. are visiting astronomers at the Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation. This work, supported by funding from NASA, is partly based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA under a NASA contract.
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Veillet, C., Parker, J., Griffin, I. et al. The binary Kuiper-belt object 1998 WW31. Nature 416, 711–713 (2002). https://doi.org/10.1038/416711a
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DOI: https://doi.org/10.1038/416711a
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