A newly discovered dwarf planet candidate, designated 2026 ED138, has been identified in the outer solar system, potentially ranking among the largest of its kind ever found. The discovery was made using observations from the Vera C. Rubin Observatory, a powerful new telescope located in Chile.
The observatory, a joint project of the U.S. National Science Foundation and the Department of Energy's Office of Science, began its 10-year sky survey in June 2026. Astronomers utilized its large digital camera to search for previously unseen celestial objects.
On October 13, astronomer Matthew Holman, using specialized software, identified ED138. Its brightness and distance from the sun suggested an unusually large size. Researchers estimate the object to be between 370 and 930 miles across. "If confirmed, ED138 would be among the largest dwarf planets ever discovered in this region of the Solar System," the observatory stated.
ED138 is currently located approximately 4.3 billion miles from the sun, placing it farther out than Pluto, which orbits at an average distance of about 3.7 billion miles. As a trans-Neptunian object, ED138 orbits the sun beyond Neptune, the solar system's farthest planet.
Scientists believe the object had previously evaded detection because it was located in a crowded region of the sky near the Milky Way, where the sheer number of stars made it difficult for earlier telescopes to identify.
The Vera C. Rubin Observatory's continuous monitoring of the southern sky, combined with advanced algorithms, enabled the team to spot ED138 within this dense stellar field.
Further observations are planned to confirm ED138's status as a dwarf planet and to determine its precise size. A dwarf planet is defined as a celestial body that orbits the sun, is massive enough to be nearly spherical, but has not cleared its orbital neighborhood of other objects. Pluto, discovered in 1930, was reclassified as a dwarf planet in 2006.
This discovery adds to recent findings that are illuminating the outer reaches of our solar system.