Astronomers using a high-powered telescope in Chile have identified a large potential dwarf planet orbiting the sun far beyond Pluto. The candidate object, provisionally designated ED138, was uncovered in data collected by the Vera C. Rubin Observatory, a facility perched on a 2,682-meter mountain that houses the world’s largest digital camera and can image the entire night sky every three days.
If subsequent observations confirm its physical characteristics, ED138 will join an elite catalog of five officially recognized dwarf planets in our solar system: Ceres, Pluto, Haumea, Makemake, and Eris. The International Astronomical Union governs the formal recognition of such bodies.
Matthew Holman, a Smithsonian senior astrophysicist and lecturer at Harvard University, first spotted the object while running a custom computer program designed to comb through billions of detections of moving objects captured by the Rubin telescope earlier in 2026. Initially reacting with what he described as “excited disbelief,” Holman immediately ran checks to rule out false positives and software glitches.
To shore up the discovery, Holman collaborated with Mario Jurić, the Rubin Solar System lead scientist and a University of Washington astronomy professor. Jurić scoured the observatory’s catalog and recovered 20 additional observations dating back to March 2026. By integrating data from other astronomical sources, researchers successfully reconstructed the object’s orbital path across a ten-year span.
Despite the robust orbital tracking, Holman emphasized that ED138’s status remains provisional. “At this point, it’s still a candidate,” Holman said. “We really need to know how physically big it is, and that will take a few months, probably.”
Estimates currently place ED138’s diameter between 600 and 1,500 kilometers, or roughly 370 to 930 miles. If the upper end of that estimate proves correct, the body would be larger than Ceres, the smallest of the recognized dwarf planets. Operating as a trans-Neptunian object, or TNO, ED138 currently orbits the sun at a distance of approximately 46 astronomical units—placing it well beyond Neptune and farther away than Pluto.
While invisible to the naked eye, the object shines brightly enough for advanced amateur astronomers to spot with proper equipment and coordinates. Scientists explain that ED138 managed to elude detection for so long because it resides in the southern celestial hemisphere, which possesses fewer sweeping survey telescopes than the north. Additionally, the object has spent the past two decades appearing to loop across the crowded stellar background of the Milky Way, where dense starfields make moving targets exceptionally difficult to isolate.
Megan Schwamb, an astrophysicist at Queen’s University Belfast and a member of the Rubin Solar System Operations team, expressed astonishment at how quickly the new telescope yielded such a major find during its commissioning phase. “I was surprised that it found such an object so early in the commissioning observations,” Schwamb stated via email, adding that the discovery highlights the observatory’s unprecedented speed, depth, and sky coverage.
Michele Bannister, an associate professor at the University of Canterbury in New Zealand who was not involved in the find, noted that ED138 sits right on the threshold of a scale where scientists begin classifying bodies as genuine worlds. While noting that any detailed surface features remain speculative until further observation or future spacecraft missions yield data, Bannister remarked that the object represents a major scientific prize for researchers studying the remote outer solar system.
If the discovery clears the verification process, the international astronomical community will eventually assign the candidate a permanent catalog number and an official name. For now, researchers are preparing follow-up observations to pin down the physical dimensions and surface composition of what may soon become our solar system’s sixth recognized dwarf planet.
