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Physical Properties
350 km
8.2e19 kg
Orbit
Eris
15.785899 d
Sources & Further Reading
Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-04-18 18:19:26.
Dysnomia is the only known moon of Eris, discovered in Keck adaptive-optics imagery in 2005. Its orbital dynamics allowed the first accurate mass determination of Eris. ALMA observations in 2018 and 2023 have refined its diameter to about 700 km, making it the second-largest known dwarf-planet moon after Charon.