Astronomers Identify New Dwarf Planet Candidate Beyond Pluto

Astronomers analyzing data from the Vera C. Rubin Observatory have identified a distant solar-system object, provisionally designated ED138, that could be classified as a dwarf planet if its size is confirmed. The object was first flagged by a computer program developed by Smithsonian senior astrophysicist Matthew Holman, who later collaborated with Rubin Solar System lead scientist Mario Jurić to locate additional observations dating back to March 2026. Using these data, the researchers traced ED138's orbit over a decade.

ED138 is estimated to be 600–1,500 kilometers in diameter and orbits the Sun at roughly 46 astronomical units, placing it farther than Pluto and categorizing it as a trans-Neptunian object. While invisible to the naked eye, it is bright enough for experienced amateur astronomers with appropriate equipment. Holman noted that the object's location in the southern sky and its passage across the dense star fields of the Milky Way have made it difficult to detect with northern-hemisphere telescopes.

The discovery adds to the Rubin Observatory's growing catalog of distant bodies. Holman cautioned that the object remains a candidate until its physical dimensions are measured, a process expected to take several months. If confirmed, the object will receive a permanent number and eventually a name, following the International Astronomical Union's naming procedures.

Michele Bannister, an associate professor at the University of Canterbury who was not involved in the discovery, described the find as scientifically significant, noting that its size places it at the threshold of being considered a world and that future observations could reveal more about its composition.