This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists may add a new dwarf planet to the official roster of our solar system. The distant, icy body, provisionally dubbed 2026 ED138, orbits our system beyond Pluto.
It was spotted earlier this month by a scientist combing through data from the Simonyi Survey Telescope at the NSF-DOE Vera C. Initial measurements place ED138 among the largest dwarf planet candidates ever discovered beyond Neptune; if confirmed, it would join the five dwarf planets recognized by the International Astronomical Union: Pluto, Ceres, Eris, Haumea and Makemake. The results were presented at a press conference today by Matthew Holman, a senior astrophysicist at the Harvard & Smithsonian Center for Astrophysics, and by Mario Jurić, a University of Washington professor of astronomy and leader of Rubin's solar system team.
Holman first spotted the candidate, and Jurić contributed additional observations. "If confirmed as a dwarf planet, ED138 would join a very small family of worlds," Holman said. "Rubin will image the whole southern sky again and again for 10 years, so any others hiding in the places earlier surveys skipped are now within reach." "Finding an object this big, roughly 1,000 kilometers (620 miles) across, is something that happens maybe once in a generation," Jurić said.
"It's the largest trans-Neptunian object found in about 20 years, and Rubin turned it up while we were still commissioning the telescope." On the evening of Oct. 13, Holman was running data collected by Rubin earlier in 2026 through a search code he developed with colleague Kevin Napier. The code is built to look at billions of detections of moving objects, compare them and find the detections that correspond to the same object. Using this method, Holman uncovered ED138, and he immediately noticed that its brightness and distance indicated that it is unusually large.
"My first reaction was one of excited disbelief," Holman said. "Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong." To remove any doubt, Jurić searched through Rubin's catalogs and images and found 20 more observations, going back to March 2026. The team also spotted ED138 in archival images from other surveys going all the way back to 2016, allowing the team to trace more than 10 years of ED138's orbit.
ED138 is currently at a distance of about 46 astronomical units (au), where 1 au is the average distance between Earth and the sun. For reference, dwarf planet Pluto orbits at an average distance of 40 au. This classifies ED138 as a trans-Neptunian object (TNO)—an object that orbits the sun at a distance greater than Neptune's.
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