The dwarf planet Eris is located about 97 astronomical units from the sun, the most remote known body in the solar system. Astronomers at Caltech discovered Eris in 2005. Caltech has measured the mass of Eris by determining the orbit of its moon Dysnomia, which is about 93 miles wide. Using the Hubble Space Telescope and adaptive optics at the Keck Observatory in Hawaii, Eris turns out to be 27% more massive than Pluto (.0028 Earth mass). Eris’s diameter appears 8% larger. It makes Eris the largest object in the Kuiper Belt and the most massive dwarf planet. Eris has the same density as Pluto and is made out of a similar mixture of rock and ice.