A distant object recorded in astronomical data for years has emerged as a promising dwarf-planet candidate. Named 2026 ED138, it was identified in observations from Chile's Vera C. Rubin Observatory and may be between 600 and 1,500 kilometers wide.
Researchers linked the object's movement across the sky using software that sifted through billions of detections. Rubin observations captured it 30 times on 20 nights from March to July 2026. Earlier images from 2016 also appear to show the same object, which had gone unnoticed because it sits against a dense field of stars near the Milky Way's plane.
A candidate awaiting confirmation
ED138 is currently about 46 astronomical units from the Sun--farther out than Pluto's average distance. Its brightness offers clues, but not a precise measurement: a small, reflective body can appear as bright as a larger, darker one. Further observations are needed to establish its size and shape.
If it is large enough to have become round under its own gravity, ED138 could meet the criteria for a dwarf planet. The International Astronomical Union currently recognizes five: Pluto, Ceres, Eris, Haumea and Makemake. The new object's status has not been confirmed.
Clues in its orbit
ED138 follows an orbit tilted nearly 25 degrees from the plane where most planets travel. Astronomers classify it as a hot-classical trans-Neptunian object; "hot" describes its orbital characteristics, not its temperature. Such paths may reflect gravitational encounters with Neptune during the solar system's early history.
Infrared measurements could help scientists estimate the object's size and surface reflectivity. Researchers may also look for a moon, whose orbit could reveal ED138's mass. Rubin's planned decade-long survey will repeatedly scan the southern sky, creating more opportunities to find distant bodies that earlier searches missed.
As follow-up observations clarify ED138's nature, Rubin's expanding survey could reshape our understanding of how many worlds inhabit the outer solar system.
