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Eris has a radius of about 1,300 km - giving a diameter of about 2,600 km.
depends on how you look at it, eris is the largest dwarf planet
The moon: area - 14,645,750 square miles; mass - 73,477,000,000,000,000,000,000 kilograms
Anywhere from a small asteroid to Earth's size, depending on the planet.