Vera C. Rubin Observatory Discovers Candidate Sixth Dwarf Planet 2026 ED138
Astronomers using the Vera C. Rubin Observatory in Chile have identified a distant, icy celestial body that may qualify as our solar system’s sixth dwarf planet. Designated 2026 ED138, the object was found during the observatory’s ongoing ten-year survey of the southern sky.
The discovery arrives two decades after Pluto lost its earlier planet status and joined a classification alongside Ceres, Eris, Haumea, and Makemake.
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
Detection and Analysis of 2026 ED138
The identification process began on the evening of October 13, when Matthew Holman, an astrophysicist at the Harvard & Smithsonian Center for Astrophysics, analyzed telescope data using software designed to detect moving objects. Holman flagged ED138 due to its brightness and the distance to the object.
Following the initial detection, researchers scoured archival data from the Rubin Observatory and other telescopes, successfully tracking the object backward in observations as far back as 2016. Subsequent calculations indicate that ED138 is an icy body with an estimated diameter between 600 and 1,500 kilometers.
While smaller than Pluto, the newly found body shares a similar scale with existing dwarf planets. To pin down its exact dimensions, researchers require supplementary observations in infrared light. Measurements show that ED138 currently orbits at a distance of roughly 46 astronomical units from the Sun, putting it beyond Pluto’s average distance of 40 astronomical units. One astronomical unit represents the approximate average distance between Earth and the Sun, or about 150 million kilometers.
Classification as a Trans-Neptunian Object
A celestial body operating in an orbit outside the planet Neptune is categorized as a trans-Neptunian object, or TNO. However, not all TNOs are dwarf planets. Official classification requires an object to possess enough mass that its own gravity has made it spherical.
Researchers emphasize the rarity of finding such a massive body during the early operational phases of a new telescope. Mario Jurić, a professor of astronomy at the University of Washington and a member of the research team, noted that uncovering a roughly 1,000-kilometer-wide object happens perhaps once per generation. It is the largest trans-Neptunian object discovered in approximately 20 years, found while the Rubin Observatory was still undergoing its commissioning phase.
“If ED138 is confirmed to be a dwarf planet, it would join a very small family of worlds,” Holman stated in a press release. The Rubin Observatory will image the entire southern sky repeatedly over a decade, bringing potential objects hidden in previously unmapped regions within reach.
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