“My first reaction was excited disbelief,” Matthew Holman said after spotting an unusual speck of light in astronomical data.
That initial signal from the night of Oct. 13, 2026, points to 2026 ED138, a potential new dwarf planet orbiting in the distant fringes of our solar system. If confirmed by further observation, the icy world beyond Neptune could rank among the largest objects ever discovered in that region, measuring roughly 370 to 930 miles across.
How Astronomers Tracked 2026 ED138 Across a Decade
Matthew Holman, a Harvard & Smithsonian astrophysicist, made the discovery while running Rubin data through a custom computer program designed to spot moving objects. When the object emerged in the automated search, Holman noted its high brightness and extreme distance.
To verify the finding, Mario Jurić, the solar system lead scientist for the Rubin project at the University of Washington, searched through additional telescope files. Jurić located 20 previous sightings captured by the Rubin Observatory between March 4 and July 11, 2026. In total, the Simonyi Survey Telescope logged the object 30 times across 20 distinct nights.
Researchers pushed the timeline back even further by searching archival images through the Asteroid Institute’s ADAM Precovery service. They found the object in digital files dating back to 2016, captured by the Dark Energy Camera on the U.S. Armed with a decade of tracking data, the research team announced the find on Oct. 27, 2026.
#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
Why Surface Reflectivity Remains Unmeasured
While the telescope data establishes an orbit sitting roughly 46 times farther from the sun than Earth does—farther out than Pluto’s average distance of about 40 times—scientists still lack a precise measurement for the object’s physical dimensions. The estimated diameter range of 600 to 1,500 kilometers relies on three primary variables: distance, brightness, and an assumed albedo, or surface reflectivity.
Because the actual reflectivity has not yet been measured, researchers cannot confirm whether the candidate sits closer to the smaller or larger end of that estimated scale. The object traces an orbital path close to the plane of the Milky Way, where millions of background stars create visual crowding that makes faint, slow-moving bodies difficult to isolate from ordinary light sources.
What Qualifies a Body as a Dwarf Planet
If subsequent studies confirm its physical characteristics, 2026 ED138 will join Ceres, Eris, Haumea, Makemake, and Pluto as the sixth recognized dwarf planet in the solar system. The dwarf planet category was established during a major astronomical debate sparked by the 2005 discovery of Eris, an icy world comparable in size to Pluto.
In 2006, the International Astronomical Union formally defined a planet as an object that orbits the sun, possesses enough mass to pull itself into a rounded spherical shape, and has cleared its immediate orbital neighborhood of other debris. A dwarf planet meets the first two criteria but fails the third, sharing its orbital zone with numerous other bodies in the Kuiper Belt—a doughnut-shaped region of icy remnants beyond Neptune.
Frequently Asked Questions About 2026 ED138
Where is the Vera C. Rubin Observatory located?
The observatory sits on Cerro Pachón in Chile.
What instrument captured the initial images?
The Simonyi Survey Telescope at the Rubin Observatory tracked the candidate dwarf planet 30 times across 20 nights using the world’s largest digital camera, the 3,200-megapixel LSST Camera.
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
How far is the object from Earth?
The candidate orbits at a distance of approximately 46 times farther from the sun than Earth does, which translates to about 4.3 billion miles away.
What makes finding objects in this region difficult?
Because the object travels along a trajectory near the crowded plane of the Milky Way, millions of background stars obscure faint moving specks, requiring specialized software to connect scattered data points across multiple nights.
More on Matthew Holman
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
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