Discovery of Dwarf Planet Candidate 2026 ED138 at the Edge of the Solar System
Researchers operating the Vera C. Rubin Observatory in Chile have discovered a potential dwarf planet designated 2026 ED138, orbiting in the distant Kuiper Belt roughly 46 times farther from the Sun than Earth. Universitetsavisa reported that the object possesses an estimated diameter between 600 and 1,500 kilometers, positioning it among the larger known bodies in the outer solar system alongside Pluto, Eris, Haumea, Makemake, and Ceres.
The discovery was unveiled during a scientific conference in Spokane, Washington, where researchers from the American Astronomical Society reviewed the initial data. Mario Juric, who leads solar system research at the Rubin Observatory, noted that 2026 ED138 is the largest found among 2,300 new objects identified beyond Pluto, according to reporting by ABC Nyheter.
Verifying the Size and Composition of 2026 ED138
Confirmation of the object’s true status requires further observation by the scientific community, specifically regarding its mass, physical dimensions, and internal composition. Under current scientific definitions established by the International Astronomical Union, a celestial body must possess enough gravitational mass to pull itself into a near-spherical shape before it can be officially classified as a dwarf planet.
Astrofysiker Matt Holman, based at the Center for Astrophysics in Cambridge, initially spotted the candidate using telescope imagery collected between March 4 and July 11, 2026, as detailed by ABC Nyheter. Holman explained that because standard optical telescopes capture sunlight reflected off passing bodies, smaller highly reflective objects can mimic the brightness of larger, less reflective ones. To resolve this ambiguity, researchers are analyzing longer light wavelengths emitted directly from the object itself to establish a precise measurement of its physical volume.
Comparing Outer Solar System Dimensions and Distances
To understand the sheer scale of the region where 2026 ED138 orbits, astronomers measure distances using Astronomical Units (AU), where 1 AU represents the distance between Earth and the Sun. Pluto, which was reclassified from a planet to a dwarf planet in 2006, orbits at approximately 40 AU. The newly identified candidate sits at roughly 46 AU, placing it firmly within the freezing expanse of the outer solar system.
While the Sun’s thin outer gas boundary extends outward to roughly 100 AU, its dominant gravitational pull reaches far beyond, stretching out toward the distant Oorts cloud between 30,000 and 80,000 AU away. The Vera C. Rubin Observatory benefits from low local humidity and minimal light pollution atop Cerro Pachón, though Holman noted that capable amateur astronomers equipped with proper instruments may eventually spot the candidate.
Frequently Asked Questions About 2026 ED138
What exact telescope captured 2026 ED138?
The discovery was made using the NSF–DOE Vera C. Rubin Observatory located on the mountain of Cerro Pachón in Chile. Researchers presented the initial findings at an American Astronomical Society meeting in Spokane, Washington.
How many dwarf planets are currently recognized in our solar system?
The International Astronomical Union currently recognizes five official dwarf planets: Pluto, Eris, Haumea, Makemake, and Ceres. If 2026 ED138 passes verification criteria regarding its mass and shape, it will become the sixth.
What separates a dwarf planet from a regular planet?
A dwarf planet must orbit the Sun and possess enough mass to form a rounded shape under its own gravity, but unlike major planets, it has not cleared neighboring debris from its orbital path.