Astronomers have identified a new dwarf planet candidate operating far beyond the orbit of Pluto, discovered through early data gathered by a powerful new telescope in Chile. Provisionally designated ED138, the distant world joins a select group of celestial bodies currently awaiting formal confirmation by the International Astronomical Union.
The discovery stems from observations made by the Vera C. Rubin Observatory, situated atop a 2,682-meter-tall mountain in Chile and equipped with the world’s largest digital camera. Having commenced operations in 2025, the telescope is capable of imaging the entire night sky every three days. Matthew Holman, a Smithsonian senior astrophysicist and lecturer in astronomy at Harvard University, utilized a computer program he co-developed to sift through vast tranches of moving-object data collected by the observatory earlier in 2026. Initially reacting with excited disbelief, Holman immediately conducted checks to rule out false positives or software errors.
To substantiate the findings, Holman collaborated with Mario Jurić, the Rubin Solar System lead scientist and a University of Washington astronomy professor. Jurić uncovered 20 additional historical observations of ED138 in the observatory’s catalog dating back to March 2026. By cross-referencing other archival data sources, the research team successfully mapped the object’s orbital path across a ten-year span.
Despite the breakthrough, Holman emphasized that ED138 holds only candidate status for now. Determining its exact physical dimensions will require several months of further study. Current estimates place the object’s diameter between 600 and 1,500 kilometers, or roughly 370 to 930 miles. If verified, those dimensions would render ED138 larger than Ceres, the smallest currently recognized dwarf planet in the solar system.
The object currently orbits the sun at a distance of approximately 46 astronomical units—placing it well beyond Pluto and classifying it as a trans-Neptunian object, or TNO. While invisible to the naked eye, the candidate is bright enough that skilled amateur astronomers with proper equipment can spot it if they know where to look. According to Holman, two main factors kept ED138 hidden from previous surveys: its location in the southern hemisphere, which limits northern telescope visibility, and its alignment with the Milky Way plane, where dense starfields make detecting moving objects exceptionally difficult.
The find represents an early triumph for the Rubin Observatory, which has been cataloging asteroids and smaller TNOs. Megan Schwamb, an astrophysicist at Queen’s University Belfast and member of the Rubin Solar System Operations team, expressed surprise at finding such a massive object during commissioning observations. She noted that the observatory’s speed, depth, and expansive sky coverage promise to revolutionize solar system exploration over the coming decade.
If ED138 achieves official confirmation, it will eventually receive a permanent numerical designation followed by a formal name. Michele Bannister, an associate professor at the University of Canterbury in New Zealand who was independent of the discovery team, called the finding scientifically compelling due to the object’s trans-Neptunian nature and substantial physical scale. While researchers currently know the object is large, Bannister noted that determining its precise surface characteristics and inner composition will require follow-up observations from other facilities.
