A possible new dwarf planet is hiding beyond Pluto — and Rubin's data just found it

Out past Neptune, in the cold dark at the edge of the solar system, the Vera C. Rubin Observatory's data may have turned up a whole new world. The object, called 2026 ED138, was spotted by Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian while running previously collected Rubin observations through search code he developed with colleague Kevin Napier, and its discovery was announced at a scientific meeting in Spokane, Washington. It appears to be between 600 and 1,500 kilometres (about 373 to 932 miles) wide — likely big enough for its own gravity to pull it into a sphere, the test that separates a dwarf planet from a mere asteroid. Only five dwarf planets are confirmed so far: Pluto, Ceres, Eris, Haumea and Makemake. Follow-up observations with the ALMA telescope in Chile should pin down its true size.