The Mass of Dwarf Planet Eris

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Science (Impact Factor: 33.61). 07/2007; 316(5831):1585. DOI: 10.1126/science.1139415
Source: PubMed


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 × 1022 � 0.02 × 1022 kilograms, or 1.27 � 0.02 that of Pluto.

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