Astronomy News
ED138: Potential New Dwarf Planet Found at the Edge of Our Solar System
This October 27, 2026, the International Astronomical Union’s Minor Planet Center (MPC) announced 2026 ED138, a large object orbiting beyond Neptune that may be a dwarf planet discovered by Vera C. Rubin Observatory. If its physical properties and classification are confirmed, it could become one of the newest dwarf planets in the Solar System.
Cr : NSF–DOE Vera C. Rubin Observatory
The Vera C. Rubin Observatory is a ground-based astronomical facility designed to repeatedly survey the sky and detect objects that move or change in brightness. Its 8.4-metre telescope is equipped with a 3.2-gigapixel camera, the largest digital camera ever built. With its wide field of view and rapid imaging, the observatory can repeatedly map the sky, helping astronomers discover asteroids,, and detect transient events such as supernovae.
Cr : NSF–DOE Vera C. Rubin Observatory
Matthew J. Holman first identified 2026 ED138 in Rubin data on October 13, 2026, while analyzing observations of moving objects. Further investigation of previous archival data showed that Rubin had recorded the object 30 times over 20 nights between March 4 and July 11, 2026. Researchers then searched archival images from the Dark Energy Camera (DECam), using the Asteroid Institute’s ADAM Precovery service to locate earlier observations dating back to 2016. Combining these observations allowed astronomers to trace the object’s orbit over more than a decade.
Current estimates place 2026 ED138 about 46 astronomical units (AU) from the Sun. One AU is the average distance between Earth and the Sun, so the object is currently around 46 times farther from the Sun than Earth is. This places it beyond Neptune and makes it a trans-Neptunian object (TNO), a group that includes Pluto, which orbits at an average distance of roughly 40 AU.
Cr : NSF–DOE Vera C. Rubin Observatory
What makes 2026 ED138 especially interesting is its estimated size. Preliminary estimates suggest that it may measure between 600 and 1,500 kilometers across. An object of this size could have enough gravity to pull itself into a nearly spherical shape, a condition known as “hydrostatic equilibrium”, making it spherical in shape and a qualification to be classified as a dwarf planet.
The International Astronomical Union currently officially recognizes five dwarf planets: Ceres, Pluto, Eris, Haumea, and Makemake. A dwarf planet must orbit the Sun and be massive enough for its own gravity to give it a nearly round shape, but it must not have cleared the neighborhood around its orbit and must not be a satellite. Although 2026 ED138’s estimated size makes it an interesting candidate, further verification is required to confirm its official status.
The discovery highlights the potential of the Vera C. Rubin Observatory’s repeated sky surveys. In April 2026, the Rubin team submitted observations of more than 11,000 asteroids to the Minor Planet Center, including roughly 380 trans-Neptunian objects. These early results offer a preview of what the observatory may reveal during its planned decade-long Legacy Survey of Space and Time (LSST). By repeatedly imaging the sky and identifying objects that have appeared in earlier observations, Rubin can help astronomers discover distant worlds that might otherwise remain unnoticed. It is of no coincidence that many discoveries are being made so early into LSST’s operations, as Vera C. Rubin goes beyond the limits of what was once beyond our capabilities. Astronomers believe that these discoveries are but a “tip of the iceberg” of more discoveries that Rubin has yet to discover.
For now, 2026 ED138 remains a candidate, a distant object at the edge of our Solar System that may offer an early glimpse of the discoveries expected from Rubin’s decade-long survey of the sky. Its discovery is a reminder that the number of known dwarf planets in the Solar System may increase substantially over the next few years.
Text: Rika Mei Reventar, Matipon Tangmatitham