The Vera C. Rubin Observatory, located in northern Chile, has announced the discovery of a significant new celestial object designated 2026 ED138. Described by the observatory team as large and bright, this icy world resides beyond the orbit of Pluto and represents the first dwarf planet candidate identified by the facility since it began its ambitious ten-year survey of the southern hemisphere sky in June. The massive telescope has already detected over 11,000 new asteroids within our solar system prior to this finding.
Initial calculations estimate the diameter of 2026 ED138 to be between 600 and 1,500 kilometers. To officially qualify as a dwarf planet, an object must possess sufficient mass for its own gravity to pull it into a rounded shape, distinguishing it from irregular asteroids. Confirming this characteristic is challenging given the object's extreme distance; current data places it 46 times farther from the Sun than Earth. The Minor Planet Center of the International Astronomical Union (IAU) confirmed these observations and announced the discovery on Tuesday.
The new object follows an orbit that takes 281 years to complete a single revolution around the Sun, with its orbital plane inclined at 25 degrees relative to the ecliptic where Earth and other planets reside. This region is home to trans-Neptunian objects, which include four of the five officially recognized dwarf planets: Pluto, Eris, Haumea, and Makemake. The fifth, Ceres, is located in the asteroid belt between Mars and Jupiter. While dozens of other candidates such as Sedna, Gonggong, Orcus, and Quaoar await official classification by the IAU, 2026 ED138 could prove to be one of the largest among them once its dimensions are refined through infrared observations.
The discovery was made on October 13 by Matthew Holman, a scientist operating from the Harvard-Smithsonian Center for Astrophysics in the United States. While processing test data from early 2026, an automated code designed to detect moving astronomical objects flagged the anomaly. Holman noted that his initial reaction was a mix of disbelief and enthusiasm, as objects of this magnitude are rare, prompting him to verify that neither he nor the software had made an error.
Subsequent analysis by Mario Jurić, the solar system research lead at the Rubin Observatory, located 30 additional observations of the object spanning from March 4 to July 11, 2026. Furthermore, archival images from the Inter-American Cerro Tololo Observatory in Chile's Coquimbo region allowed researchers to reconstruct the object's trajectory back to 2016. The team explains that 2026 ED138 had previously gone unnoticed because it traverses a section of the sky crowded with millions of stars, effectively hiding it against the bright background of the Milky Way for most telescopes.
The Rubin Observatory's advanced capabilities in both real-time detection and retrospective identification are transforming the speed and precision with which astronomers can determine orbits and understand the distant solar system. If ongoing studies confirm that 2026 ED138 has a rounded shape, it may be recognized as a dwarf planet by the IAU. This would follow the precedent set twenty years ago on August 24, 2006, when the organization reclassified Pluto based on its inability to gravitationally dominate its orbital neighborhood.
Sources: El País Ciencia.