Rubin Observatory Finds a Possible Dwarf Planet 46 Times Farther From the Sun Than Earth

Astronomers using the Vera C. Rubin Observatory have identified what may be a new dwarf planet orbiting the Sun beyond Neptune, a body provisionally named 2026 ED138 that could be about 1,000 kilometers across. If confirmed, it would be the largest object found in the outer solar system in about 20 years.

The discovery was announced at a press conference by Matthew Holman, a senior astrophysicist at the Harvard & Smithsonian Center for Astrophysics, and Mario Jurić, a University of Washington astronomy professor who leads the solar system team for the NSF–DOE Vera C. Rubin Observatory. The findings are preliminary, and no peer-reviewed paper has been reported.

The object sits about 46 astronomical units from the Sun, where one unit is the average Earth-Sun distance. Pluto averages about 40. From its distance, brightness and estimated surface reflectivity, the team puts its diameter between 600 and 1,500 kilometers, or roughly 370 to 930 miles. Icy bodies of that size are expected to be round, which is the key requirement for dwarf-planet status. The team says further observations are needed to pin down its size and confirm the classification.

Holman found it on October 13 while searching data Rubin collected earlier this year with software he developed with colleague Kevin Napier, which compares billions of detections of moving objects to link those belonging to the same body. The brightness and distance suggested something unusually large. Jurić then searched Rubin's catalogs and found 20 more observations dating to March 2026, and the team traced the object in archival images from other surveys going back to 2016, giving them more than a decade of its orbit. ED138 lies near the plane of the Milky Way, where millions of stars make faint moving objects hard to pick out, which likely explains why earlier surveys missed it.

Holman described his first reaction as 'excited disbelief,' saying he immediately checked whether he or his code had made an error. Jurić said finding an object this large is something that happens 'maybe once in a generation.' Holman added that if ED138 is confirmed, it 'would join a very small family of worlds.' That family currently has five recognized members: Pluto, Ceres, Eris, Haumea and Makemake.

The find is among the first results of Rubin's full survey. The Legacy Survey of Space and Time formally began in June 2026. In April, before it started, the team reported more than 11,000 new asteroids, including roughly 380 new trans-Neptunian objects, and called that 'the tip of the iceberg.' Rubin will image the entire southern sky repeatedly over 10 years, and Jurić highlighted its ability to 'precover' objects, searching older images once something is identified to refine its orbit.

Scientists study bodies like this to learn how the solar system formed, how giant planets migrated and how smaller objects were scattered along the way. Holman noted that Rubin's decade of coverage could reveal other large objects in regions that earlier surveys skipped. The team has also made the object's path explorable through the Orbitviewer app.