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Published June 15, 2007 | Supplemental Material
Journal Article Open

The Mass of Dwarf Planet Eris


The discovery of dwarf planet Eris was followed shortly by the discovery of its satellite, Dysnomia, but the satellite orbit, and thus the system mass, was not known. New observations with the Keck Observatory and the Hubble Space Telescopes show that Dysnomia has a circular orbit with a radius of 37,350 ± 140 (1-σ) kilometers and a 15.774 ± 0.002 day orbital period around Eris. These orbital parameters agree with expectations for a satellite formed out of the orbiting debris left from a giant impact. The mass of Eris from these orbital parameters is 1.67 × 10^(22) ± 0.02 × 10^(22) kilograms, or 1.27 ± 0.02 that of Pluto.

Additional Information

© 2007 American Association for the Advancement of Science. Received 29 December 2006; accepted 14 March 2007. This research is supported by a Presidential Early Career Award to M.E.B. In addition, E.L.S. is supported by a NASA graduate student research fellowship. We thank J. Aycock, R. Campbell, A. Conrad, K. Grace, J. Lyke, C. Melcher, C. Sorenson, M. van Dam, and C. Wilburn at Keck Observatory, without whom these complicated LGS AO observations would not have been possible.

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