Astronomers announced the discovery of 2026 ED138, a massive icy body orbiting the Sun beyond Pluto that measures between 600 and 1,500 kilometers across. Identified in observational data from the Vera C. Rubin Observatory, the object could become the solar system’s sixth officially recognized dwarf planet.
Located roughly 46 times farther from the Sun than Earth, the distant candidate was surfaced by an advanced algorithm running against data gathered by the NSF–DOE Vera C. Rubin Observatory. The icy world sits comfortably past Pluto’s average distance of about 40 astronomical units. If follow-up observations confirm its dimensions, it will join a very small, exclusive group of worlds.
If confirmed as a dwarf planet, ED138 would join a very small family of worlds.
Matthew Holman, Center for Astrophysics | Harvard & Smithsonian
Rubin Observatory Finds 2026 ED138 in Existing Data
Matthew Holman, a Rubin Operations team member and in-kind contributor from the Center for Astrophysics | Harvard & Smithsonian, spotted the candidate on October 13, 2026. The discovery came from applying powerful software to data the telescope had already collected. He was running observations gathered between March 4 and July 11, 2026, through a search algorithm designed to trace faint moving points of light against dense fields of background stars.
My first reaction was one of excited disbelief.
Matthew Holman, Center for Astrophysics | Harvard & Smithsonian
Those initial checks involved combing through a massive catalog to rule out software errors or false alarms. The Simonyi Survey Telescope captured the candidate 30 separate times across 20 nights during that initial window. Further archival searches revealed that the Dark Energy Camera on the Víctor M. Blanco 4-meter Telescope in Chile had inadvertently photographed the object in prior years, extending its known orbital track back across a decade.
Size Estimates and Albedo Leave Dwarf Planet Status Unconfirmed
A distant world’s brightness depends entirely on two variables: its actual physical size and its albedo, or how effectively its icy surface reflects sunlight. While the object’s brightness and distance point to a giant scale, astronomers cannot formally classify it as a dwarf planet without pinning down its exact physical dimensions. A smaller, highly reflective body can easily appear just as bright in telescope images as a much larger, darker object.
Initial analysis places the candidate’s diameter between 600 and 1,500 kilometers. According to Mario Jurić, a University of Washington researcher and Rubin Solar System Lead Scientist, the official roster managed by the International Astronomical Union has not admitted a new member since 2008. Several other large bodies, including Quaoar and Gonggong, are widely studied as dwarf planets in scientific literature despite sitting outside that official five-member list of Pluto, Ceres, Eris, Haumea, and Makemake.
The Vera Rubin Observatory is located in Chile. The Minor Planet Center is responsible for cataloging these objects, and archival images extending back to 2016 helped astronomers trace its orbit. ED138 was comparatively luminous, indicating either that it is unusually large, unusually reflective, or both.
Infrared Follow-Up Observations Will Reveal New Details
Resolving the ambiguity around 2026 ED138 requires looking past visible light into infrared wavelengths. Because icy bodies in the outer solar system emit a faint thermal glow in the infrared spectrum, researchers look to space-based assets like NASA’s James Webb Space Telescope to measure thermal emissions directly and settle the size debate once and for all.
Rubin will image the whole southern sky again and again for 10 years, so any others hiding in the places earlier surveys skipped are now within reach.
Matthew Holman, Center for Astrophysics | Harvard & Smithsonian
With the ten-year Legacy Survey of Space and Time now underway, astronomers expect the observatory to uncover thousands of similar worlds previously lost in the frozen depths beyond Neptune.
Did we find a new dwarf planet?@VRubinObs has revealed a new dwarf planet candidate that orbits our Sun beyond Pluto! And it may be among the largest and brightest objects discovered in this region of the Solar System: https://t.co/mPcVYVhvXZ pic.twitter.com/d94196aMuT
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#ICYMI: our Solar System has a newly-discovered dwarf planet candidate! Meet 2026 ED138, recently revealed by NSF–DOE Rubin Observatory ☄Let's get to know this new world a little bit, shall we?https://t.co/wTOg898zBu pic.twitter.com/RC0HP5rZiL
Meet our Solar System's newest dwarf planet candidate: 2026 ED138!Orbiting past Pluto, scientists found it in NSF–DOE Rubin Observatory data from earlier in 2026. Early analysis suggests it's 600–1500 km across, one of the largest found past Neptune!🔗 https://t.co/wTOg898zBu pic.twitter.com/hEgnk597rl
NSF–DOE @VRubinObs Discovers New Dwarf Planet Candidate in Our Solar SystemThe candidate, provisionally designated 2026 ED138, was found by scientists working to improve Rubin's algorithms that search for distant moving objects in our Solar System.🔗 https://t.co/OPIC57K0m4 pic.twitter.com/Qx9zBCkAmm