Rubin Observatory spots large dwarf planet candidate
The icy object, provisionally named ED138, sits roughly 46 astronomical units from the Sun and was found in data from the Simonyi Survey Telescope.
28 Oct 2026 0 reads Compiled with AI
Scientists using data from the Vera C. Rubin Observatory have identified a large object beyond Pluto that could be a new dwarf planet, provisionally named ED138. The body orbits the Sun at about 46 astronomical units. It is a trans-Neptunian object and could join the five known dwarf planets.
Size and brightness
If confirmed, ED138 would be one of the largest trans-Neptunian bodies found in the past two decades. Its brightness, combined with its distance, points to an unusually large size. Estimates based on these measurements put its diameter between 600 and 1,500 kilometres.
The object was spotted by senior astrophysicist Matthew Holman, who ran a search algorithm on billions of moving-object detections. He and University of Washington professor Mario Jurić later found 20 more observations, going back to March 2026. Archival images from other surveys, some dating to 2016, let the team trace more than ten years of the object's orbit. Holman developed the code with colleague Kevin Napier and first ran it on data collected earlier in 2026.
Observatory strengths
The discovery shows what the observatory can do. Its camera is the largest ever built, and its rapid, wide-field imaging lets it scan the southern sky again and again over a decade. Powerful data-analysis tools sift through millions of points of light, spotting moving objects that earlier surveys skipped. In April the team announced observations of more than 11,000 new asteroids, including about 380 new trans-Neptunian objects. The telescope's regular monitoring also revealed ED138 in a crowded region near the plane of the Milky Way, where many objects have been lost among stars.
Other telescopes can now make follow-up observations to refine ED138's orbit and measure its exact size, which is needed to confirm whether it is a dwarf planet. The public can view its path on Orbitviewer, a web app that lets students and teachers explore the outer solar system in three dimensions. The app also gives an intuitive way to see where ED138 sits in our cosmic backyard.