Rubin Observatory spots possible sixth dwarf planet, 2026 ED138, beyond Pluto

A candidate found in archival data

The Vera C. Rubin Observatory in Chile has picked up a possible new dwarf planet, provisionally named 2026 ED138. Matthew Holman, the researcher credited with the find, spotted an unusually bright but distant object on 13 October in data the observatory had collected in early 2026. He then analysed the material further to rule out mistakes. The findings were presented at a press conference that also featured Mario Jurić, who carried out follow-up observations.

Size and distance

The estimated diameter is 600 to 1,500 km. One report gives about 1,000 km instead. Ceres, the smallest recognised dwarf planet, measures 963 km, so 2026 ED138 may be larger. Spiegel Online puts the object at about 46 astronomical units from the Sun, compared with 40 for Pluto, while Blick gives a distance of 6.7 billion km.

2026 ED13846

Pluto40

2026 ED138

46 AU

Pluto

40 AU

Data from the article text

An object of this size and composition almost always forms a sphere. A dwarf planet is defined as massive enough for its own gravity to make it round, but unlike a planet it has not cleared smaller objects from its orbit. Five dwarf planets are currently recognised by the International Astronomical Union: Pluto, Ceres, Eris, Haumea and Makemake. Ceres lies in the asteroid belt, while the others orbit beyond Neptune.

Why it stayed hidden

ED138 lies near the plane of the Milky Way, a region crowded with millions of stars, which makes it hard to pick out a moving object. Many large telescopes are located in the Northern Hemisphere, and ED138 can only be seen from south of the equator. Its orbit over a period of ten years was determined from observations reaching back to 2016. Twenty further observations, going back to 4 March 2026, were found in catalogues and images.

What confirmation requires

Official dwarf planet status depends on settling the object's shape and size, after which it is expected to receive a formal name. Jurić said the object is the largest trans-Neptunian object found in about 20 years and that Rubin detected it while the telescope was still being brought into operation. Holman said the observatory will photograph the entire southern sky repeatedly over the next ten years, which could reveal other bodies hidden in areas earlier surveys skipped.