Astronomers have discovered a possible new dwarf planet orbiting beyond Pluto, potentially adding another world to the solar system’s small group of officially recognized dwarf planets.
The icy object, provisionally designated 2026 ED138, was identified using observations from the Vera C. Rubin Observatory in Chile. According to the observatory’s official announcement, the discovery was announced on October 27 and could represent one of the largest dwarf planet candidates found beyond Neptune.
The newly discovered object is estimated to measure between 600 and 1,500 kilometers (370–930 miles) in diameter and currently sits approximately 46 times farther from the Sun than Earth. For comparison, Pluto’s average distance from the Sun is around 40 times that of Earth. As Reuters reports, additional observations will be necessary to establish the object’s exact size and determine whether it qualifies as a dwarf planet.
The discovery was made by astronomer Matthew Holman of the Harvard & Smithsonian Center for Astrophysics, who identified the object on October 13 while analyzing telescope data collected earlier this year. Researchers subsequently uncovered additional observations dating back to March 2026, along with archival images from as early as 2016. According to the University of Washington, these findings allowed scientists to trace more than a decade of the object’s orbital history.
One reason the object remained undiscovered for so long is its location against a particularly crowded region of the Milky Way, where millions of background stars make detecting distant moving objects difficult. Rubin Observatory’s powerful telescope and advanced detection algorithms enabled researchers to distinguish the object from the surrounding stars. Scientists also found that its orbit is tilted nearly 25 degrees relative to the solar system’s main orbital plane, suggesting that gravitational interactions with Neptune may have altered its trajectory billions of years ago.
If confirmed, 2026 ED138 would join the five dwarf planets currently recognized by the International Astronomical Union: Pluto, Ceres, Eris, Haumea, and Makemake. Unlike full-sized planets, dwarf planets have not cleared their orbital neighborhoods of other objects. Researchers believe ED138 may be massive enough for its gravity to pull it into a nearly spherical shape, but infrared observations are still needed to establish its physical characteristics and confirm its classification.
The discovery also highlights the potential of Rubin Observatory’s ongoing ten-year survey of the southern sky. Earlier this year, the observatory reported observations of more than 11,000 previously unknown asteroids, including hundreds of distant objects beyond Neptune. As detailed by the U.S. National Science Foundation, the observatory’s ability to repeatedly scan enormous portions of the sky could reveal many more previously undetected objects, helping astronomers better understand the formation and evolution of our solar system.
