Astronomers say they may have found a new dwarf planet in the far reaches of our Solar System, beyond the orbit of Pluto. Called 2026 ED138, the potential dwarf planet is big and bright, astronomers say, and if confirmed, would be one of the largest dwarf planets ever seen in that part of the Solar System. It was discovered by the Vera C. Rubin Observatory, which has the world’s largest digital camera and has just begun its groundbreaking study of the sky. Artist’s impression of a planet orbiting binary stars. Credit: dottedhippo/Getty Images How 2026 ED138 was found 2026 ED138 is a trans-Neptunian object, meaning it orbits the Sun well beyond Neptune, the most distant planet from the Sun in our Solar System. It was found in observations made during preparations for the Vera C. Rubin Observatory’s Legacy Survey of Space and Time, which is a 10-year study of the southern sky. The discovery was made by Matthew Holman, a member of the Rubin Operations team at the Center for Astrophysics | Harvard and Smithsonian. On October 13, 2026, Holman was analyzing data collected by Rubin earlier in the year. NSF-DOE Vera C. Rubin Observatory on the summit of Cerro Pachón in Chile. Credit: NSF-DOE Vera C. Rubin Observatory I was using a search code that analyzes billions of detections of moving objects in space, compares them, and then locates detections that correspond to the same object. Holman discovered ED138 and noted that its brightness and distance revealed that it is unusually large. “The Rubin Observatory’s superpower is the ability to clearly capture motion and change among a large number of objects and phenomena that humans have never seen before,” says Edward Ajhar, NSF program director for the Rubin Observatory. “That power greatly expands our ability to reveal and understand new things about our Solar System, the Milky Way, and billions of other galaxies across the Universe.” “My first reaction was excited disbelief,” Holman says. “Objects like this are very rare, so I immediately started checking to see if I or the code had done something wrong.” Pluto, the most famous dwarf planet in our Solar System, was reclassified in 2006. Credit: NASA/JHUAPL/SwRI What we know so far ED138 could be among the largest and brightest bodies scientists have ever found in the outer regions of the Solar System. It is currently about 46 astronomical units (AU) from the Sun, where 1 AU is the average distance between the Earth and the Sun. Pluto, for comparison, orbits the Sun at an average distance of 40 AU. ED138’s orbit is inclined almost 25 degrees to the plane of the Solar System, which astronomers say makes it a “hot classical trans-Neptunian object.” Its inclined orbit also suggests that it was perturbed from its original orbit due to gravitational interactions with Neptune. Image showing the orbital path of dwarf planet candidate 2026 ED138 (ED138). Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA. Acknowledgment: Image Processing: M. Jurić (UW), D. de Martin, and M. Zamani (NSF NOIRLab) By analyzing ED138’s distance from the Sun, its brightness, and how reflective its surface is, astronomers estimate that it is between 600 and 1,500 km (370 and 930 miles) across. ED138 was found in a region of sky near the plane of our Milky Way galaxy. It’s a region packed with millions of stars, which likely explains why the dwarf planet candidate has eluded detection by most telescopes until now. However, the Rubin Observatory has been regularly and continuously monitoring the entire southern hemisphere sky since it became operational. That, combined with algorithms that examine millions to billions of points of light in the sky, allowed the team to detect ED138. The orbit of dwarf planet candidate ED138 is inclined relative to the plane of the Solar System. Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/R. Attorney. Image processing: M. Zamani (NSF NOIRLab). Orbit data provided by the IAU Minor Planet Center (MPCorb catalog), funded by NASA PDCO and the Tamkin Foundation. Star Map: NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC. A new dwarf planet? The most famous dwarf planet in our Solar System is probably Pluto, which was reclassified from a planet to a dwarf planet by the International Astronomical Union in 2006. The reclassification of Pluto came about because, as astronomers began to learn more and more about the outer reaches of the Solar System, they discovered that Pluto is just one of many similar bodies in that distant region, far from the Sun. The ‘planet’ was reclassified as a dwarf planet along with other bodies such as Haumea, Makemake and Eris, which are located at the edge of the Solar System, but also Ceres and Vesta, which are among the largest bodies in the asteroid belt between Mars and Jupiter, much closer to the Sun. However, not all trans-Neptunian objects are dwarf planets; To be classified as such, a dwarf planet must be massive enough that its own gravity gives it a round shape. The orbit of ED138 in relation to the other dwarf planets in our Solar System. Credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/R. Attorney. Image processing: M. Zamani (NSF NOIRLab). Orbit data provided by the IAU Minor Planet Center (MPCorb catalog), funded by NASA PDCO and the Tamkin Foundation. Star Map: NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC. Preliminary analysis shows that ED138 is among the largest dwarf planets ever discovered beyond Neptune, provided its status is confirmed. Astronomers say infrared observations will be needed to confirm its size and whether it is a dwarf planet. “If ED138 is confirmed to be a dwarf planet, it would join a very small family of worlds,” Holman says. “Rubin will image the entire southern sky over and over again for ten years, so any others hiding in places previously missed are now within reach.”
