New Dwarf-Planet Candidate 2026 ED138 Discovered Beyond Pluto

Scientists using the Vera C. Rubin Observatory in Chile have identified an icy body beyond Pluto that may qualify as a dwarf planet. The object, temporarily designated 2026 ED138, is estimated to be 370–930 miles (600–1,500 km) across and orbits at roughly 46 AU from the Sun. Initial imaging captured the object on 30 observations across 20 nights between March 4 and July 11 2026.

The Straits Times

The International Astronomical Union (IAU) defines a dwarf planet as a body that orbits the Sun, has enough mass for a roughly spherical shape, and has not cleared its orbital neighbourhood. Objects larger than about 600 km in diameter are generally considered massive enough to become spherical, placing ED138 among the largest candidates observed in the distant solar system.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• March 4 2026 – First Rubin images of the region captured.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• July 11 2026 – Final Rubin images in the initial data set recorded.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• October 27 2026 – Matthew Holman and Mario Juric presented their findings at the DPS meeting in Washington.

New Scientist

• October 28 2026 – Public announcement of the discovery released.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• Diameter: 370–930 mi (600–1,500 km).

New Scientist

• Orbital distance: ~46 AU.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• Orbital period: ~281 years.

New Scientist

• Orbital inclination: ~25° to the ecliptic.

New Scientist

• Observational coverage: 30 detections on 20 nights.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

Matt Holman of the Center for Astrophysics, Harvard & Smithsonian, said confirming the object’s size is the next priority, noting Rubin captures reflected sunlight while longer-wavelength facilities such as ALMA can detect thermal emission. Mario Juric, Rubin Solar-System Lead Scientist at the University of Washington, highlighted the observatory’s ability to locate objects in archival images, improving orbit determinations. Both described the find as evidence that Rubin’s speed, depth and precision are expanding the inventory of distant solar-system bodies.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

• “The main thing we need to do is to establish the physical size of 2026 ED138,” — Matt Holman

The Straits Times

• “Rubin is giving us an unprecedented capacity to explore the sky through a combination of speed, depth, and precision,” — Mario Juric

New Scientist

If confirmed as a dwarf planet, ED138 would join a small, exclusive club of distant, icy worlds that preserve clues about the early solar system. Its size and tilted orbit suggest past gravitational interactions with Neptune, offering a case study for models of planetary migration and the scattering of trans-Neptunian objects.

Vera C. Rubin Observatory may have discovered one of the largest dwarf planets hidden beyond Pluto

Researchers plan to use the Atacama Large Millimeter/submillimeter Array (ALMA) to measure thermal emission, helping distinguish between a small, highly reflective object and a larger, darker one. Continued monitoring by Rubin over its ten-year Legacy Survey of Space and Time will enable detection of additional distant objects that may also qualify as dwarf planets.

The Straits Times