Rubin Observatory finds a possible dwarf planet beyond Pluto, designated 2026 ED138

Scientists using the NSF–DOE Vera C. Rubin Observatory in Chile have found a large, bright object beyond Pluto that they have identified as a dwarf planet candidate. The International Astronomical Union's Minor Planet Center (MPC) announced the object, provisionally designated 2026 ED138, on October 27, 2026, the U.S. National Science Foundation (NSF) and the observatory said. If confirmed, it would join the five dwarf planets the IAU recognizes: Pluto, Ceres, Eris, Haumea and Makemake.

Rubin researchers Mario Jurić of the University of Washington, the observatory's solar system lead scientist, and Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian presented the result at the 58th annual Division for Planetary Sciences meeting in Spokane, Washington.

How it was found

On the evening of October 13, Holman ran data that Rubin had collected earlier in 2026 through a search code he developed with his colleague Kevin Napier. The code compares billions of detections of moving objects to find the ones that belong to the same body. The object's brightness and distance suggested at once that it was unusually large, the observatory said.

Jurić then found 20 more observations in Rubin's catalogs and images. In all, Rubin's Simonyi Survey Telescope recorded the object 30 times on 20 nights between March 4 and July 11, 2026. Archival images from the Dark Energy Camera on the NSF Victor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory, found through the Asteroid Institute's ADAM Precovery service, extended the record back to 2016. That gave the team more than 10 years of the object's orbit.

The orbit, compared with Pluto

One astronomical unit (au) is the average distance between Earth and the Sun. ED138 is now about 46 au away, which makes it a trans-Neptunian object (TNO), one of the bodies that orbit beyond Neptune. Its orbit is tilted almost 25 degrees (24.5 degrees in the MPC's solution) from the plane of the solar system. That makes it a hot classical TNO, which suggests that gravitational encounters with Neptune pushed it off its original path, the observatory said.

Why it is only a candidate

Under the IAU's 2006 definition, as NASA summarizes it, “a dwarf planet is an object in orbit around the Sun that is large enough to pull itself into a nearly round shape but has not been able to clear its orbit of debris.” The team's size estimate comes from the object's distance, brightness and estimated surface reflectivity (albedo). Icy bodies of 600 to 1,500 km are expected to be round. But infrared observations are needed to pin down its size and confirm that it is a dwarf planet.

The object sits in a part of the sky close to the plane of the Milky Way, crowded with millions of stars, which is likely why it went undiscovered until now. Rubin's repeated scans of the whole southern sky, combined with algorithms that pick moving points out of millions to billions of light sources, allowed the team to spot it.

What comes next

Astronomers elsewhere can now plan follow-up observations. Rubin's 10-year Legacy Survey of Space and Time began in June 2026. Even before that, in April, the Rubin solar system team reported more than 11,000 new asteroids to the MPC, including roughly 380 new TNOs. “Rubin will image the whole southern sky again and again for ten years, so any others hiding in the places earlier surveys skipped are now within reach,” Holman said.