Astronomers at the Vera C. Rubin Observatory announced the discovery of a large candidate dwarf planet designated 2026 ED138, orbiting in the distant Kuiper Belt beyond Neptune, ScienceAlert reported on October 27, 2026. The object measures between 600 and 1,500 kilometers across, placing it among the largest trans-Neptunian bodies identified yet in the outer solar system.
How Harvard Astrophysicists Spotted ED138
The discovery emerged from data collected by the Vera C. Rubin Observatory and processed through search code developed by Matthew Holman and Kevin Napier of the Center for Astrophysics | Harvard & Smithsonian. Holman noted that his first reaction was one of excited disbelief given the rarity of such objects. When Holman and Mario Jurić of the University of Washington checked further, they recovered 30 observations from Rubin spanning March to July 2026, according to Scientific American.
Why This Distant World Remained Hidden for a Decade
Despite being bright enough for capable observers to see, 2026 ED138 evaded detection because it was hiding within one of the brightest parts of the night sky, the Milky Way. The candidate dwarf planet was positioned directly against the densely populated stellar backdrop of the Milky Way galaxy, where the surrounding starlight drowned it out, according to NSF reporting.
Comparing ED138 to the Known Dwarf Planets
If confirmed by subsequent infrared observations to determine its mass and round shape, 2026 ED138 would join Pluto, Ceres, Eris, Haumea, and Makemake as the sixth recognized dwarf planet in the solar system, as detailed by the National Science Foundation.
What Astronomers Will Investigate Next
Researchers require additional telescope imaging to pin down the exact reflectivity and size of 2026 ED138, which will clarify whether its self-gravity is sufficient to pull it into the spherical shape required for official dwarf planet classification, WGBH reported. Meanwhile, the Vera C. Rubin Observatory will continue its ten-year Legacy Survey of Space and Time across the southern sky, a project expected to uncover thousands of additional outer solar system bodies and potentially address hypotheses regarding Planet Nine, as outlined by SLAC National Accelerator Laboratory.
Questions About the Newly Discovered Candidate
Why was the object missed by earlier surveys?
As noted by the National Science Foundation, the object was located in a region of the sky crowded with millions of stars near the Milky Way plane, and its orbit is tilted by 24.5 degrees relative to the rest of the solar system.
What telescope instrument captured the discovery?
According to SLAC National Accelerator Laboratory, the observations were captured by the 3.2-gigapixel camera at the NSF–DOE Vera C. Rubin Observatory located on Cerro Pachón in Chile.
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
More on Rubin Observatory
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
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