Astronomers Discover Large New Dwarf Planet Candidate Beyond Pluto

Astronomers announced the discovery of a distant dwarf planet candidate in our solar system on Tuesday, marking one of the largest trans-Neptunian objects found in 2 decades.

The icy body, provisionally designated 2026 ED138, was spotted earlier this month by scientists analyzing data collected by the Simonyi Survey Telescope at the NSF-DOE Vera C. Rubin Observatory in Chile.

Initial measurements place the diameter of 2026 ED138 between 600 and 1,500 kilometers, making it one of the largest objects ever identified in the outer solar system.

If confirmed by the International Astronomical Union, the distant object would join an exclusive roster of recognized dwarf planets that currently includes Pluto, Ceres, Eris, Haumea and Makemake.

Scientists study such distant bodies to understand how the solar system formed and how giant planets migrated over time.

"If confirmed as a dwarf planet, ED138 would join a very small family of worlds," said Matthew Holman, a senior astrophysicist at the Harvard and Smithsonian Center for Astrophysics.

Holman first identified the object on the evening of Oct. 13 while running telescope data through a specialized search code developed with colleague Kevin Napier.

"My first reaction was one of excited disbelief," Holman said, adding that he immediately began checking whether he or the computer code had made a mistake.

To verify the discovery, Mario Jurić, a University of Washington astronomy professor and leader of the Rubin solar system team, searched archival images and catalogs to trace more than 10 years of the object's orbit.

"Finding an object this big, roughly 1,000 kilometers across, is something that happens maybe once in a generation," Jurić said.

The object was hidden within the crowded background of the Milky Way plane, which is why earlier sky surveys failed to detect it.

The Rubin Observatory sits at a distance where its large mirror and wide field of view allow it to image the entire southern sky repeatedly.

Researchers plan to conduct further observations to measure the exact size of 2026 ED138 and confirm its status.