Scientists discover potentially massive dwarf planet candidate hiding beyond Pluto

The discovery, announced on October 27, was made using observations from the Vera C. Rubin Observatory, a newly operational facility jointly funded by the U.S. National Science Foundation and the Department of Energy's Office of Science. The observatory began its 10-year sky survey in June 2026, utilizing the world's largest digital camera to search for previously unseen objects in our solar system.

Size and Location

Researchers identified the object as 2026 ED138 and estimated it measures between 370 and 930 miles across. Currently located about 4.3 billion miles from the sun, it orbits farther than Pluto, which sits at an average distance of approximately 3.7 billion miles from our star.

Discovery Process

On October 13, astronomer Matthew Holman was using computer software he developed with colleague Kevin Napier to search through telescope data when he spotted the object. "Using this method, Holman uncovered ED138, and he immediately noticed that its brightness and distance indicated that it is unusually large," the observatory explained.

Holman described his reaction as "one of excited disbelief." He added, Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong.

Challenges and Future

The object had remained undetected for so long because it was hiding in a crowded region of the sky near the Milky Way, where millions of stars made it difficult for earlier telescopes to spot. The Rubin Observatory's regular monitoring of the entire Southern Hemisphere sky, combined with powerful algorithms, enabled the discovery.

Scientists now plan to conduct further observations to determine ED138's exact size and whether it qualifies as a dwarf planet. "If confirmed as a dwarf planet, ED138 would join a very small family of worlds," Holman noted, adding that the observatory's 10-year survey will likely reveal more such objects.

A dwarf planet is defined as a celestial body that orbits the sun and is large enough to be nearly round, but unlike a full-sized planet, it shares its orbital region with other objects it has not gravitationally cleared away. Pluto was reclassified as a dwarf planet in 2006 after being considered the ninth planet since its discovery in 1930.