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Moon count, as of September 2026
How many moons does Eris have?
1 known moon.
Eris has 1 known moon as of September 2026, according to NASA and the JPL Solar System Dynamics group.
The named moons
Sorted by size. Distance is the average distance from the centre of Eris.
| Moon | Diameter (miles / km) | Distance (miles / km) | One orbit | Discovered |
|---|---|---|---|---|
| Dysnomia | 382 / 615 | 23,200 / 37,273 | 15.79 days | 2005, Keck Observatory |
Why the number keeps changing
Big moons were found centuries ago through telescopes. The small ones, often only a few kilometres across, are found today by long camera exposures on the largest telescopes and by spacecraft. Each new batch is announced by the Minor Planet Center, so the count goes up in jumps. That is why every count on this site carries a date.