Researchers have identified a new candidate for a dwarf planet in the Kuiper Belt, located beyond Pluto. The object, designated 2026 ED138, measures between 600 to 1,500 kilometers (373 to 932 miles) across and lies within Pluto’s orbital range. This discovery was made using data from the Vera C. Rubin Observatory, which is expected to significantly enhance our understanding of the outer Solar System.
Matthew Holman, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, described his initial reaction to the find as one of “excited disbelief.” Holman was analyzing the observatory’s data when he noticed something unusual: a previously unknown large object moving through the Kuiper Belt. The team tracked ED138 through 30 detections over 20 nights between March and July 2026.
The discovery is notable because ED138 may be one of the largest entities identified in trans-Neptunian space, potentially rivaling the sizes of known dwarf planets Makemake and Haumea. The object orbits the Sun roughly every 281 years, reaching distances of about 36.86 astronomical units at its closest and 49.04 astronomical units at its farthest. For comparison, Pluto’s orbit ranges from about 29.6 to 49.08 astronomical units.
Despite sharing an orbital range with Pluto, ED138’s unique characteristics contributed to its evasion from previous observations. Its orbit is tilted by approximately 24.5 degrees relative to the Solar System’s plane, complicating detection efforts. Additionally, the object was obscured against the bright star field of the Milky Way, making it harder to identify among numerous stars.
The Rubin Observatory, which features the largest digital camera ever built for astronomy, began its decade-long survey of the southern sky in June 2026. The observatory’s camera can capture an area equivalent to about 40 full moons in one exposure, allowing scientists to detect faint celestial objects that previous telescopes could not. The project aims to identify thousands of previously unknown objects in the outer Solar System.
Future observations, particularly in infrared wavelengths, will be crucial in determining ED138’s actual size and establishing whether it qualifies as a dwarf planet. As researchers continue to analyze historical data from archives, intriguing possibilities about the outer Solar System may soon come to light, including insights into the hypothetical Planet Nine, a proposed large body believed to influence the orbits of some distant trans-Neptunian objects.
Holman emphasized the potential of the Rubin Observatory to reveal more hidden objects over the next ten years. “Any others hiding in the places earlier surveys skipped are now within reach,” he stated.
