A distant object called 2026 ED138 may be up to 1,500 kilometers wide, placing it among the largest known bodies outside Neptune’s orbit. Astronomers are now working to confirm its size, shape, and status as a possible dwarf planet.
The object lies farther from the Sun than Pluto. Its estimated diameter would make it roughly comparable in size to Makemake, another dwarf planet in the outer solar system. However, the upper estimate remains uncertain.
“2026 ED138 could be as large as 1,500 kilometers in diameter.”
That wording reflects an important limit in the current evidence. Researchers have not yet confirmed the object’s exact dimensions or whether it meets every condition required for dwarf-planet classification.
Size Estimate Draws Attention
Objects at such great distances receive little sunlight and can appear as faint points through telescopes. Astronomers often estimate their size by measuring brightness and making assumptions about surface reflectivity.
A bright object may be relatively small with a reflective surface. A darker body may need to be much larger to produce the same apparent brightness. This uncertainty can leave early diameter estimates with a wide range.
At the reported upper limit, 2026 ED138 would be smaller than Pluto, which is about 2,377 kilometers across. It could still rank near Makemake and Haumea, though Haumea has an elongated shape that complicates direct comparisons.
Its possible scale also raises questions about its internal structure. Large icy bodies can have enough gravity to pull themselves into rounded forms, one of the central tests for dwarf-planet status.
Classification Requires More Evidence
Under the International Astronomical Union’s definition, a dwarf planet must orbit the Sun and have enough mass to become nearly round. It must not be a moon, and it must not have cleared other objects from its orbital region.
Researchers will therefore need more than a diameter estimate. Key questions include:
- Whether 2026 ED138 has a nearly round shape
- How accurately its orbit can be measured
- Whether it has any moons
- How reflective its surface is
- Whether the estimated diameter can be narrowed
A moon could help astronomers calculate the object’s mass by tracking the satellite’s orbit. Without one, determining mass and density can be harder.
A Crowded Outer Solar System
Pluto’s reclassification in 2006 created the modern dwarf-planet category. The decision reflected growing evidence that Pluto belongs to a large population of icy objects rather than standing alone at the solar system’s edge.
Five bodies are officially recognized as dwarf planets: Ceres, Pluto, Eris, Haumea, and Makemake. Several other distant objects are treated as strong candidates, but classification can remain unsettled for years because direct observations are difficult.
2026 ED138 may add another major member to that group. Yet its reported size should be treated as preliminary until follow-up observations refine its brightness, reflectivity, orbit, and shape.
The next steps will likely depend on repeated telescope measurements and possible observations at infrared wavelengths. Those results could show whether 2026 ED138 is a large, dark body or a smaller, brighter one. Confirmation of a rounded shape would strengthen the case for dwarf-planet status and expand scientists’ picture of how large icy worlds formed far from the Sun.
