# New dwarf planet? Rubin Observatory finds 2026 ED138, a world up to 1,500 km wide beyond Pluto > Hidden in the crowded star fields of the Milky Way, ED138 is the largest object found beyond Neptune in about 20 years, and could become the sixth recognised dwarf planet. - Publisher: NextDiff (https://nextdiff.com/) - Section: Hardware - Author: NextDiff Editorial - Published: 2026-10-29T05:16:51.999Z - Updated: 2026-10-29T05:16:51.999Z - Canonical URL: https://nextdiff.com/posts/new-dwarf-planet-2026-ed138-rubin-observatory/ - Topics: space, astronomy, dwarf-planets, rubin-observatory ## In short The NSF–DOE Vera C. Rubin Observatory announced a new dwarf planet candidate, 2026 ED138, on 27 October 2026. The icy object orbits about 46 au from the Sun, beyond Pluto, and is estimated at 600 to 1,500 km across. If infrared observations confirm it is round, it would become the sixth recognised dwarf planet. ## Key takeaways - Rubin Observatory found 2026 ED138, a large trans-Neptunian object about 46 au from the Sun, and the Minor Planet Center announced it on 27 October 2026. - Its size is estimated at 600 to 1,500 km; Rubin's solar system lead calls it the largest object found beyond Neptune in about 20 years. - It is a candidate, not a confirmed dwarf planet: infrared observations are needed to pin down its size and show it is round. - It hid near the plane of the Milky Way, where millions of stars swamp faint moving objects. Rubin's software picked it out of billions of detections. Our Solar System may have a sixth dwarf planet. The NSF–DOE Vera C. Rubin Observatory has found **2026 ED138**, a large, bright icy world orbiting beyond Pluto, and scientists have named it a **new dwarf planet** candidate. The International Astronomical Union's Minor Planet Center announced the object on 27 October 2026, and the team estimates it is 600 to 1,500 km across. That would make it [the largest object found beyond Neptune in about 20 years](https://noirlab.edu/public/news/noirlab2626/), according to Rubin's solar system lead, Mario Jurić of the University of Washington. ![3D model of 2026 ED138's orbit with the orbits of Pluto, Eris, Haumea, Makemake and Ceres](/media/b10534b643f540ef8fc6.jpg) *Image: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/R. Proctor; image processing M. Zamani (NSF NOIRLab) (CC BY 4.0)* ## What was found? ED138 is a trans-Neptunian object, meaning it circles the Sun farther out than Neptune. It is currently about **46 au** from the Sun (1 au is the Earth–Sun distance). Pluto's average distance is about 40 au. Its orbit is tilted almost 25 degrees from the plane of the planets. Rubin's team says that makes it a "hot classical" object, one that was probably knocked off its original path by Neptune's gravity long ago. Rubin has not measured its size directly. The 600–1,500 km range comes from how bright it looks, how far away it is and a guess at how reflective its surface is. Jurić puts it at "roughly 1,000 kilometers" and called a find this big something that happens "maybe once in a generation", as [Phys.org reported](https://phys.org/news/2026-10-rubin-observatory-reveals-dwarf-planet.html). ![Chart comparing 2026 ED138's estimated 600 to 1,500 km size with Pluto, Eris, Haumea, Makemake and Ceres](/media/018f7dde93814f41a387.jpg) *Chart: NextDiff, from Rubin/NOIRLab estimates and Wikipedia* ## How did Rubin find the new dwarf planet? On the evening of 13 October, Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian ran data Rubin had collected earlier in 2026 through search code he wrote with Kevin Napier. The code compares billions of detections of moving points of light and links the ones that belong to the same object. One link stood out: something too bright for its distance. "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." It was real. Jurić went back through Rubin's catalogues and found more sightings: in all, Rubin's Simonyi Survey Telescope saw ED138 **30 times on 20 nights** between 4 March and 11 July 2026. Archival images from the Dark Energy Camera in Chile, found with the Asteroid Institute's precovery service, pushed the record back to 2016. That gave the team more than ten years of orbit. ![Mosaic of Rubin Observatory discovery images showing 2026 ED138 moving between March and July 2026](/media/815932403838408d982d.jpg) *Image: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA; image processing M. Jurić (UW), D. de Martin & M. Zamani (NSF NOIRLab) (CC BY 4.0)* ## Why was it missed until now? ED138 sits close to the plane of the Milky Way, a part of the sky packed with millions of stars. A faint dot moving slowly among them is easy to lose. Rubin photographs the whole southern sky every few nights, so its software can spot a dot that shifts while the stars stay put. ![2026 ED138's path across a crowded star field near the Milky Way, March to July 2026](/media/ede49a6efc5a4b629620.jpg) *Image: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA; image processing M. Jurić (UW), D. de Martin & M. Zamani (NSF NOIRLab) (CC BY 4.0)* This is the payoff Rubin was built for. Before its ten-year Legacy Survey of Space and Time (LSST) formally began in June, the team had already reported more than 11,000 new asteroids, including about 380 new trans-Neptunian objects. ED138 was found in data from that early run-up period. Wide sky surveys keep producing surprises: earlier this month ESA's Euclid telescope found a comet by accident (see our story on [Euclid's new comet](/posts/euclid-new-comet-c-2026-s1-esa/)). ## Is it officially a dwarf planet yet? No. To count as a dwarf planet, an object must be massive enough for its own gravity to pull it round. Icy bodies of ED138's estimated size are expected to be round, but nobody has shown it yet. Infrared observations are needed to measure its true size, and from that, its likely shape. If it passes, ED138 joins the five dwarf planets the IAU recognises: **Pluto, Ceres, Eris, Haumea and Makemake**. It would also get a proper name; "2026 ED138" is a provisional designation. ## Why it matters Objects in the outer Solar System are a fossil record. Their sizes, orbits and surfaces show how the giant planets migrated and scattered smaller bodies billions of years ago. A large object on a tilted orbit is a useful clue to that history. It also says something about what's still out there. "Rubin will image the whole southern sky again and again for ten years," Holman said, "so any others hiding in the places earlier surveys skipped are now within reach." You can follow ED138's orbit in 3D on [Orbitviewer](https://orbitviewer.app/en/solar-items/2026-ed138/). ## Questions readers ask ### Is there a new dwarf planet in 2026? Possibly. On 27 October 2026 the Rubin Observatory announced 2026 ED138 as a dwarf planet candidate. It is not confirmed yet: astronomers still need infrared observations to measure its size and show it is round. ### How big is 2026 ED138? The team estimates 600 to 1,500 km across, based on its brightness, distance and an assumed surface reflectivity. Pluto, for comparison, is about 2,377 km wide. ### How far away is 2026 ED138? About 46 astronomical units from the Sun, or roughly 46 times the Earth–Sun distance. Pluto's average distance is about 40 au. ### What makes something a dwarf planet? It orbits the Sun, is massive enough for its own gravity to pull it into a round shape, and has not cleared its orbit of other objects. Size is used as a clue to roundness, but it must be confirmed by observation. ### How many dwarf planets are there? The International Astronomical Union recognises five: Pluto, Ceres, Eris, Haumea and Makemake. If confirmed, ED138 would be the sixth. ## Sources - [NOIRLab / Rubin Observatory: Rubin reveals its first dwarf planet candidate in our Solar System (noirlab2626)](https://noirlab.edu/public/news/noirlab2626/) - [University of Washington via Phys.org: Rubin Observatory reveals its first dwarf planet candidate](https://phys.org/news/2026-10-rubin-observatory-reveals-dwarf-planet.html) - [Scientific American: Rubin may have just discovered our solar system's sixth dwarf planet](https://www.scientificamerican.com/article/the-vera-c-rubin-observatory-may-have-just-discovered-our-solar-systems-sixth-dwarf-planet/) - [Reuters via US News: Possible new dwarf planet identified orbiting beyond Pluto](https://www.usnews.com/news/world/articles/2026-10-28/possible-new-dwarf-planet-identified-orbiting-beyond-pluto) - [Gizmodo: Rubin spots possible dwarf planet beyond Pluto, the biggest in 20 years](https://gizmodo.com/rubin-observatory-spots-possible-dwarf-planet-beyond-pluto-the-biggest-in-20-years-2000831865) - [Orbitviewer: 2026 ED138 interactive orbit](https://orbitviewer.app/en/solar-items/2026-ed138/)