Rubin Observatory Spots Potential Sixth Dwarf Planet Beyond Neptune
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The Vera C. Rubin Observatory has identified object 2026 ED138, a body estimated at 600–1,500 km across in a distant region of the solar system beyond Neptune's orbit and about 46 times Earth's distance from the Sun — one of the largest dwarf planet candidates yet detected. Further observations are required to confirm whether it qualifies as a dwarf planet.
Astronomers using the Vera C. Rubin Observatory have announced the discovery of a dwarf planet candidate designated 2026 ED138, which could become the sixth official member of that category, joining Pluto, Eris, Ceres, Haumea and Makemake. The find was made by running vast amounts of Rubin Observatory data through a search code developed by Matthew Holman and Kevin Napier, both of the Center for Astrophysics at Harvard and Smithsonian. When Holman and colleague Mario Jurić of the University of Washington checked the results, they found 30 Rubin observations of the object dating from March to July 2026, and additional sightings from other sources stretching back to 2016. Those combined data allowed the team to begin mapping the object's orbit. 2026 ED138 sits about 46 astronomical units from the Sun — making it more remote than Pluto, which orbits at roughly 40 AU — and its path is tilted approximately 25 degrees off the solar system's plane, a tilt that may reflect past gravitational disruption by Neptune. Its estimated diameter of 600 to 1,500 kilometres makes it one of the largest dwarf planet candidates detected so far. However, further observations are still needed to establish whether the object has enough mass to pull itself into a spherical shape, a key requirement for dwarf planet classification. The discovery was possible in part because the Rubin Observatory's powerful instruments can pick out objects hidden against the star-crowded backdrop of the Milky Way.
