Astronomers have found a possible new dwarf planet hiding beyond Pluto, and it may be among the largest objects ever discovered in that distant region of the solar system.
The object, provisionally named 2026 ED138, was announced on 27 October 2026 by the International Astronomical Union’s Minor Planet Center. It was spotted in data from the NSF-DOE Vera C. Rubin Observatory in Chile, whose Simonyi Survey Telescope houses the world’s largest digital camera.
Bigger than Ceres?
ED138 is currently about 46 astronomical units from the Sun — one astronomical unit is the average distance between Earth and the Sun — compared with Pluto’s average distance of about 40. That makes it a trans-Neptunian object, an object that orbits the Sun beyond Neptune.
Based on its distance, brightness and estimated surface reflectivity, the team estimates its size at between 600 and 1,500 kilometres across. If confirmed, that would make it bigger than Ceres, the smallest of the five dwarf planets recognised by the International Astronomical Union, and among the largest dwarf planet candidates ever found beyond Neptune.
Found in a crowded sky
The discovery was made by Matthew Holman, a senior astrophysicist at the Harvard and Smithsonian Center for Astrophysics, who was running data collected by Rubin earlier in 2026 through a search code he developed with colleague Kevin Napier. On the evening of 13 October, ED138 popped up, and Holman said his first reaction was “excited disbelief”.
His colleague Mario Juric, a University of Washington professor and leader of Rubin’s solar system team, searched the catalogues and found 20 more observations going back to March 2026. In all, Rubin recorded ED138 30 times on 20 nights between 4 March and 11 July 2026, and researchers were later able to plot its orbit back about 10 years.
The object was found in a region of sky close to the plane of the Milky Way, a crowded field packed with millions of stars, which is one reason it stayed hidden for so long.
Not a dwarf planet yet
ED138 is a candidate, not a confirmed dwarf planet. Astronomers must confirm that it is large enough for its own gravity to pull it into a round shape, and that will probably take a few months of further observations, likely in infrared light to pin down how reflective its surface is. If confirmed, it would join Pluto, Ceres, Eris, Haumea and Makemake as only the sixth recognised dwarf planet, and it would eventually receive a permanent number and a real name.
Sources: Rubin Observatory announcement, 27 Oct 2026; University of Washington News, 27 Oct 2026; CNN via KION, 28 Oct 2026.
