Vera C. Rubin Observatory Spots Icy Candidate Beyond Pluto
Researchers leveraging a Chilean telescope have spotted an icy body traveling beyond Pluto that could potentially become part of the solar system’s limited group of dwarf planets. Designated 2026 ED138, the candidate possesses an estimated diameter between 600 and 1,500 kilometers and orbits about 46 times farther from the sun than Earth.
The discovery emerged from data collected by the US National Science Foundation and US Department of Energy Vera C. Rubin Observatory on Cerro Pachón mountain in central Chile. Operating since 2025, the telescope is capable of imaging the entire sky every three days. Utilizing a jointly created software program to sift through information gathered by Rubin, Harvard astronomy lecturer and Smithsonian senior astrophysicist Matthew Holman identified the entity prior to verifying its orbital path with University of Washington researcher and Rubin Solar System Lead Scientist Mario Jurić, who object before confirming its trajectory with Mario Jurić, who works at the University of Washington and serves as Rubin Solar System Lead Scientist.
Additional archival inspection proved instrumental in establishing the object’s path. Further digging revealed that the Dark Energy Camera on the Víctor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile also spotted 2026 ED138, with observations going back to 2016. The discovery was announced at a scientific meeting in Spokane, Washington.
Physical Classifications and Comparative Scaling
If confirmed by the International Astronomical Union, 2026 ED138 would join a very small family of worlds. The global authority currently recognizes five dwarf planets: Pluto, Eris, Haumea, and Makemake in the distant trans-Neptunian region, alongside Ceres in the main asteroid belt between Mars and Jupiter. Current data indicates 2026 ED138 would rank among the largest dwarf planets.
ED138 is bigger than the smallest recognized dwarf planet, Ceres. Establishing official dwarf planet status requires proof that an object possesses sufficient mass for its own gravity to pull it into a round shape. While 2026 ED138 appears to have sufficient mass to meet this requirement, exact physical verification remains underway.
Reflectivity complicates visual measurements. Because optical telescopes only capture sunlight reflected from the object, a smaller, more reflective body can show the same amount of light as a larger, less reflective one. Resolving this ambiguity demands observations at longer wavelengths.
Observational Hurdles and Next-Phase Measurements
Pinpointing the exact physical dimensions of 2026 ED138 requires shifting from reflected optical light to thermal emission detection. Holman explained that by looking at longer wavelengths, with an observatory like ALMA—the Atacama Large Millimeter/submillimeter Array based in Chile—scientists can detect the light emitted by the object itself to help measure its size. Infrared light observations, representing the specific spectral range tailored for NASA’s James Webb Space Telescope, will likewise prove essential for pinning down the exact dimensions of 2026 ED138.
Detection itself was constrained by positioning. The candidate is in the southern hemisphere and is on the same plane as our galaxy, which made it very difficult to observe from the northern hemisphere.
What Remains Unknown About 2026 ED138
The International Astronomical Union has not yet assigned a permanent number or formal name to the candidate. Holman remarked that while naming suggestions have already poured in, many are already taken by other objects.
Observers await further observations to confirm whether 2026 ED138 definitively meets the physical thresholds required to hold its ground alongside established dwarf planets.
