Rubin Observatory Detects Possible New Dwarf Planet Beyond Pluto

The Vera C. Rubin Observatory, funded by the U.S. National Science Foundation and the U.S. Department of Energy, reported the detection of a distant solar-system body called 2026 ED138, located beyond Pluto’s orbit. The object was identified by astronomer Matthew Holman of the Center for Astrophysics while analyzing Rubin data collected earlier in the year.

Holman said his initial reaction was “one of excited disbelief” and that he immediately verified the detection to rule out errors in the software. Subsequent review of Rubin images from March to July confirmed the object's presence in more than 20 observations.

Based on its brightness, distance and assumed reflectivity, researchers estimate the object's diameter to be between 600 and 1,500 kilometres. Objects of that size are expected to be rounded by their own gravity, a key requirement for dwarf-planet status, though further observations are needed to confirm its shape.

The discovery adds to a rapidly expanding catalog of solar-system bodies uncovered with Rubin data. Prior to the start of the main ten-year Legacy Survey of Space and Time, the observatory had already reported over 11,000 new asteroids and submitted roughly one million observations to the International Astronomical Union’s Minor Planet Center.

Rubin’s survey, which began on 30 June 2026, will repeatedly image the southern sky for a decade, generating an estimated 30 million gigabytes of data. Among its goals are a comprehensive inventory of solar-system objects, studies of the Milky Way, and investigations of dark matter and dark energy.

Holman noted that the find illustrates the potential for further discoveries, stating, “For me, the main significance of 2026 ED138 is that it demonstrates that there are still exciting discoveries to be made,” and expressed confidence that future observations will clarify whether the object meets the International Astronomical Union’s definition of a dwarf planet.