Astronomers at the Vera Rubin Observatory in Chile have spotted an object beyond Neptune's orbit that could be the sixth dwarf planet discovered to date.
The object, currently dubbed 2026 ED138, is likely between 600 and 1500 kilometers (373 to 972 miles) wide, according to astronomers. That means it's probably big enough to have spun itself into a sphere, which is one of the primary requirements to meet the definition of a "dwarf planet."
If 2026 ED138 is closer to its minimum estimated size of 600 km, it is roughly one-quarter the diameter of Pluto. If it is closer to the maximum estimate of 1,500 km, it would be about two-thirds the size of Pluto, making it a substantial trans-Neptunian object.
🚨BREAKING: A possible new dwarf planet has been discovered beyond Pluto Discovery announced October 27. Astronomers using the Vera C. Rubin Observatory have identified an object designated 2026 ED138, a candidate for dwarf-planet status. https://t.co/wA3bqb688h
— The MARTIAN 🚀 (@ab_ray10) October 28, 2026
The five dwarf planets discovered to date include Pluto, Ceres, Eris, Haumea, and Makemake.
ED138 is 46 astronomical units (Earth's distance from the Sun, or 93 million miles per AU), or about 4.25 billion miles from the Sun. The object is about 1.5 billion miles farther from the Sun than Pluto.
ED138 was discovered by Matthew Holman on October 13, when he was running a search code through some Rubin Observatory data with his colleague Kevin Napier. "That search revealed a mysterious object beyond Neptune's orbit," writes Space.com's Mike Wall. "Despite its immense distance from the sun, this body was relatively bright, suggesting that it's larger than the average trans-Neptunian object."
"My first reaction was one of excited disbelief," Holman said in a statement on Tuesday, the day the discovery of 2026 ED138 was announced. "Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong."
The Rubin Telescope has operated for only about a year and a half. But it's been able to map an extraordinary number of stars in that time.
The Vera Rubin Observatory sits atop Cerro PachĂłn, an 8,799-foot-tall (2,682 meters) mountain in northern Chile, and features a primary mirror 28 feet (8.4 m) wide. The scope achieved first light in April 2025 and began its main project, the 10-year-long Legacy Survey of Space and Time (LSST), in June of this year.
During the LSST, Rubin images the entire southern sky every few days using a 3.2-gigapixel camera, the largest digital camera ever built for astronomy. This work creates a high-resolution time-lapse "movie" that can reveal a great deal about the cosmos.
For example, astronomers think Rubin will shed light on dark energy and dark matter, the mysterious stuff that together makes up most of the universe's mass-energy budget. Its observations will also serve as a solar system inventory, helping scientists map out our cosmic backyard like never before. Rubin has already discovered more than 11,000 new asteroids, for example, with many more surely to come.
If confirmed, ED138 would join the five dwarf planets recognized by the International Astronomical Union: Pluto, Ceres, Eris, Haumea, and Makemake. #2026ED138 #ED138 #DwarfPlanet #TransNeptunianDwarfPlanets #TransNeptunianObjects https://t.co/fL4ZJ13SI1
— Mashable India (@MashableIndia) October 28, 2026
There is still much to learn about the object, however. For example, we won't know whether or not it's a dwarf planet until astronomers nail down its size. And that will require observations in infrared light, the range of wavelengths that NASA's James Webb Space Telescope is optimized for.
So stay tuned: There's doubtless more news about 2026 ED138 coming, and Rubin could turn up more worlds like it in the coming months and years.
"If confirmed as a dwarf planet, ED138 would join a very small family of worlds," Holman said. "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."
This is truly the Golden Age of Astronomy, and the discoveries by the ever more sophisticated robotic machines we put in space have only scratched the surface of the wonders we'll behold in the coming years.
