Rubin Observatory finds its first dwarf planet candidate, 2026 ED138, beyond Pluto
The NSF–DOE Vera C. Rubin Observatory has produced its first dwarf planet candidate, a large, bright trans-Neptunian object designated 2026 ED138 that orbits beyond Pluto and may rank among the largest such candidates ever found.
The NSF–DOE Vera C. Rubin Observatory has turned up its first dwarf planet candidate: a large, bright trans-Neptunian object now designated 2026 ED138. Matthew Holman found the object on October 13, 2026, and the International Astronomical Union’s Minor Planet Center announced it on October 27, giving it a formal designation two weeks after it first showed up in the data.
The object orbits beyond Pluto, and the observatory puts its estimated diameter somewhere between 612 and 1,530 km. That is an unusually wide range. Sizes for distant bodies like this are typically inferred from how much sunlight they reflect, so a smaller, highly reflective surface and a larger, darker one can look equally bright from Earth. Pinning down where 2026 ED138 actually falls inside that window will take follow-up work. Even the low end of the range, though, describes a substantial body, and the high end would put it in genuinely rare company.
That is the point the National Science Foundation emphasized: 2026 ED138 may be one of the largest dwarf planet candidates ever found, and if its status is confirmed, it would join the five recognized dwarf planets: Pluto, Ceres, Eris, Haumea, and Makemake. Four of those five sit in the outer solar system, and the list has stayed short for a reason. Objects big enough to qualify are few, and those far beyond Neptune are faint, slow-moving, and easy to miss.
The word “candidate” is doing real work here. Being designated by the Minor Planet Center means the object’s orbit has been recorded and accepted, not that anyone has settled its physical nature. Dwarf planet status hinges on properties such as whether a body is massive enough to have pulled itself into a roughly round shape, and for something this distant that usually has to be argued from size and brightness rather than observed directly. A diameter estimate that spans more than a factor of two leaves plenty of room for that argument to go either way.
The broader significance is the source of the find. Rubin was built to survey the sky repeatedly and catch things that move, and the outer solar system is exactly where that capability matters most. A large, bright object beyond Pluto that went unrecorded until now is a fair indication of how much the observatory’s data still holds, and of the kind of discoveries that will likely keep arriving as more of it is combed through.
For now, 2026 ED138 is a designation, an orbit, and a size range. The next round of observations will narrow that range, and with it the question of whether the solar system’s short list of dwarf planets is about to get one name longer.