Rubin Observatory finds dwarf planet candidate 2026 ED138

The Vera C. Rubin Observatory has detected a large, bright object orbiting in the outer Solar System beyond Pluto, WIRED.jp reports wired.jp. The object was given the provisional designation 2026 ED138 (ED138) and is considered a dwarf planet candidate. It may turn out to be one of the largest dwarf planets found in this region so far wired.jp.

Matthew Holman of the Harvard-Smithsonian Center for Astrophysics, who worked on improving the search algorithm, found ED138 on October 13. The code compares billions of detections of moving objects and identifies those that belong to the same body wired.jp. To rule out an error, the team checked catalogs and images. They found that the Simonyi Survey Telescope at the Rubin Observatory had observed ED138 30 times over 20 nights, from March 4 to July 11, 2026 wired.jp.

How the object was found

The team also analyzed earlier images from the Dark Energy Camera (DECam), built by the US Department of Energy. These gave data on ED138 going back to 2016, so its orbit can now be traced over more than ten years wired.jp.

The object lies close to the plane of the Milky Way, among millions of stars. According to the report, most telescopes lose it against the background sources, which probably explains why it was not found earlier. Rubin regularly and continuously surveys the whole southern sky and has an algorithm for picking small moving objects out of a vast number of light points wired.jp.

Orbit and size

ED138 is currently about 46 au from the Sun; Pluto's mean distance is 40 au. Objects orbiting beyond Neptune are called trans-Neptunian objects (TNOs). The orbit of ED138 is inclined about 25 degrees to the plane of the Solar System and may have been disturbed by gravitational interaction with Neptune wired.jp.

From the object's distance, brightness and estimated surface reflectivity, the team puts its size at 600–1,500 km. An icy body this large is expected to be round, but narrowing the size requires infrared observations or observations of a stellar occultation wired.jp. If confirmed, ED138 would join the five dwarf planets recognized by the IAU: Pluto, Ceres, Eris, Haumea and Makemake wired.jp.

In April, before the Legacy Survey of Space and Time began in June 2026, the team submitted about one million observations to the Minor Planet Center. They included data on more than 11,000 newly found asteroids, about 380 of them TNOs wired.jp. Images of ED138 are available to data rights holders on the Rubin Science Platform, and the orbit can be viewed in 3D in the Orbitviewer app wired.jp.

Vera C. Rubin Observatory finds dwarf planet candidate 2026 ED138 beyond Pluto, estimated at 600–1,500 km

How the object was found

Orbit and size

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