NSF–DOE Vera C. Rubin Observatory has spotted 2026 ED138, a large, bright trans-Neptunian object that scientists have identified as a dwarf planet candidate, the observatory said in an Oct. 27 release. The International Astronomical Union Minor Planet Center announced the discovery the same day in a Minor Planet Electronic Circular under the provisional designation 2026 ED138.
Senior astrophysicist Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian, a Rubin Operations team member, first flagged the object on Oct. 13 in earlier 2026 Rubin data using a search code developed with colleague Kevin Napier, according to the release. Rubin's Simonyi Survey Telescope observed ED138 30 times on 20 nights between March 4 and July 11, and archival images from other surveys extend the arc back to 2016, covering more than 10 years, according to the release and University of Washington News.
ED138 is currently about 46 astronomical units from the Sun, farther than Pluto's average of about 40 au, the release said. An astronomical unit is the average Earth-Sun separation. New Scientist reported an orbit of about 281 years tilted about 25 degrees from the solar system's plane. The team estimates a diameter of 600 to 1,500 kilometers based on distance, brightness and estimated reflectivity; icy bodies this large are expected to be round, though infrared observations are still needed to confirm dwarf-planet status, according to the release.