Scientists have identified a distant icy object beyond Pluto that could potentially be classified as a new dwarf planet, expanding the known family of such bodies in the solar system. The object, designated 2026 ED138, was detected using the Vera C. Rubin Observatory, situated atop Cerro Pachón in Chile, a facility operated through a collaboration between the U.S. National Science Foundation and the Department of Energy.
Estimated to measure between approximately 600 and 1,500 kilometers (370 to 930 miles) in diameter, 2026 ED138 orbits the sun at a distance roughly 46 times that of Earth’s distance from the sun. By comparison, Pluto's orbit lies at an average of about 40 times Earth’s distance from the sun. If confirmed as a dwarf planet, 2026 ED138 would rank among the largest known members of this category.
Currently, the International Astronomical Union (IAU), the body responsible for defining and classifying celestial objects, recognizes five dwarf planets: Pluto, Eris, Haumea, Makemake—all located beyond Neptune—and Ceres in the asteroid belt between Mars and Jupiter. The discovery of 2026 ED138 would increase that count and further enrich understanding of the solar system’s outer region.
Astrophysicist Matt Holman, affiliated with the Center for Astrophysics at Harvard & Smithsonian and credited with the object’s discovery, highlighted the significance of this finding. He noted that the Rubin Observatory’s capabilities have opened new opportunities for detecting previously unknown objects in the solar system’s distant, frigid zones.
Determining whether 2026 ED138 qualifies as a dwarf planet depends on further observations. According to the IAU’s criteria, a dwarf planet must be massive enough for its gravity to shape it into a nearly round form. Current data suggest 2026 ED138 may meet this requirement, but uncertainties remain regarding its precise size and reflectivity.
Holman explained that the measurements obtained from the Rubin Observatory indicate the amount of sunlight reflected by the object, which can correspond either to a smaller, highly reflective surface or a larger, less reflective one. Establishing its actual dimensions is critical for confirming its classification.
The discovery underscores ongoing efforts in planetary astronomy to explore and understand the solar system’s outer reaches, a region populated by numerous icy bodies whose characteristics are still being revealed. Further monitoring and study of 2026 ED138 will clarify its composition and status, potentially adding a significant new member to the roster of dwarf planets.