New Rubin Observatory Finds Candidate Dwarf Planet Beyond Pluto
Astronomers using the Vera C. Rubin Observatory have detected an icy body, designated 2026 ED138, orbiting far beyond Pluto, which could be classified as a dwarf planet pending further observations.
Scientists operating the Vera C. Rubin Observatory on Cerro Pachón in Chile have identified an icy object, 2026 ED138, that orbits roughly 46 astronomical units from the Sun, slightly farther than Pluto's average distance of about 40 astronomical units. The object's estimated diameter ranges from 600 to 1,500 kilometres, placing it among the larger known dwarf planets if its classification is confirmed.
The Rubin telescope, a collaborative project of the U.S. National Science Foundation and the U.S. Department of Energy, first spotted the object, and researchers say additional measurements are required to verify its status as a dwarf planet. Confirmation would add the object to the International Astronomical Union's current list of five dwarf planets—Pluto, Eris, Haumea, Makemake and Ceres.
"For me, what this demonstrates is that many exciting discoveries remain to be made with the Rubin Observatory and other telescopes," said astrophysicist Matt Holman of the Center for Astrophysics, Harvard & Smithsonian, who led the detection.
Holman noted that determining the object's physical size is a priority, explaining that observations of reflected sunlight can be ambiguous because a smaller, more reflective body can appear as bright as a larger, darker one. He added that longer-wavelength observations with facilities such as the Atacama Large Millimeter/submillimeter Array (ALMA) could measure the object's own thermal emission, helping to resolve its dimensions.
The discovery was presented at a scientific meeting in Spokane, Washington.