Nov 10, 2026 · 12 min
A Hidden Outer-Solar-System World Comes Into View
Help! This new dwarf planet needs a name
2026 ED138 could expand the known population of dwarf planets and reveal how much of the outer solar system remains unexplored.
- 1Scientists need thermal infrared observations and stellar occultations to confirm ED138’s size, shape, and dwarf-planet status.
- 2Its reddish surface offers clues about its exterior, but not whether the object’s interior is icy.
- 3The object’s discovery suggests one to three similarly bright worlds may still await detection, with many fainter ones farther out.
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Matthew Holman explains how an object can remain hidden for decades when it occupies the southern sky and crosses the crowded Milky Way.
The brief
The Vera Rubin Observatory has brought 2026 ED138 into view beyond Neptune, but its provisional status depends on confirming that the object is large enough to become spherical.
Matthew Holman explains why brightness cannot establish a dwarf planet’s size, and how thermal infrared observations and stellar occultations can provide the missing measurements.
ED138 appears reddish and may be comparable in scale to Pluto, but its color reveals something about the surface—not whether its interior is icy.
The object escaped earlier detection because its southern-sky position limited historical observations and its path through the crowded Milky Way obscured it among background stars.
Holman estimates that one to three objects as bright as ED138 may remain undiscovered, while much fainter worlds could make the outer solar system far more populous.
The episode ends with the provisional designation 2026 ED138 and a naming process that invites ideas inspired by creation myths or hidden things coming into view.
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