A potential new dwarf planet has been discovered beyond Pluto, offering astronomers a glimpse of a distant world that may be among the largest objects identified in the outer solar system in decades.
Using observations from the NSF–DOE Vera C. Rubin Observatory, researchers identified the object, provisionally designated 2026 ED138, and estimated that it measures between 600 and 1,500 kilometers (370 and 930 miles) across.
On October 13, astrophysicist Matthew Holman of the Center for Astrophysics, Harvard & Smithsonian, identified the object while analyzing data collected by Rubin earlier this year. Its unusual brightness and distance suggested that it could be large enough to qualify as a dwarf planet.
If confirmed, ED138 could join Pluto, Ceres, Eris, Haumea, and Makemake as one of the five dwarf planets officially recognized by the International Astronomical Union (IAU).
“If confirmed as a dwarf planet, ED138 would join a very small family of worlds,” Holman said in a statement. “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.”
Holman and Mario Jurić, a University of Washington professor of astronomy and Rubin’s solar system lead scientist, presented the findings at a press conference during the 58th Annual Division for Planetary Sciences meeting in Spokane, Washington.
A hidden new world
“Finding an object this big, roughly 1,000 kilometers (620 miles) across, is something that happens maybe once in a generation,” Jurić said. “It’s the largest trans-Neptunian object found in about 20 years, and Rubin turned it up while we were still commissioning the telescope.”
ED138 is 46 times farther away from the Sun than Earth, and currently sits 46 astronomical units (AU) from our star than Earth. By contrast, Pluto’s orbital distance is 40 AU.
The newfound object belongs to a population of distant bodies known as trans-Neptunian objects (TNOs), which orbit the Sun beyond Neptune. These objects offer important clues about the solar system’s early history, including how giant planets moved and how gravitational interactions scattered objects to the farthest reaches of our cosmic neighborhood.
Qualifications for being a dwarf planet
Under the International Astronomical Union’s definition, a dwarf planet must orbit the Sun, possess enough mass for its gravity to pull it into a nearly round shape, and not have cleared its orbital neighborhood of other objects. It also cannot be a satellite.
Reviewing the newly obtained data, astronomers found that, based on the object’s brightness, distance, and estimated surface reflectivity, the object could be between 600 and 1,500 kilometers across. However, more observations are needed to understand its dimensions.
“My first reaction was one of excited disbelief,” Holman said. “Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong.”
How the object was found
Holman identified ED138 using a computer algorithm developed with fellow astrophysicist Kevin Napier. The software searches through billions of detections, comparing observations of moving objects to determine which measurements correspond to the same celestial body.
After the initial discovery on October 13, researchers began searching existing observations to confirm the object’s identity and better understand its orbit. Jurić searched Rubin’s archival data and image catalogs to help verify the discovery, uncovering 20 more images dating back to March 2026 that helped correlate their findings.
In total, Rubin’s Simonyi Survey Telescope had observed ED138 30 times across 20 nights between March 4 and July 11.
“Rubin is giving us an unprecedented capacity to explore the sky through a combination of speed, depth and precision,” Jurić said. “And the discovery is just the beginning: Once we identify a new object, we can search back months, and sometimes even decades, finding it in images where nobody knew to look.
“This ability to both discover and ‘precover’ objects is transforming how quickly and accurately we can determine their orbits and understand the distant solar system,” Jurić added.
Chrissy Newton is a PR professional and the founder of VOCAB Communications. She currently appears on The Discovery Channel and Max and hosts the Rebelliously Curious podcast, which can be found on YouTube and on all audio podcast streaming platforms. Follow her on X: @ChrissyNewton, Instagram: @BeingChrissyNewton, and chrissynewton.com. To contact Chrissy with a story, please email chrissy @ thedebrief.org.