Scientists have identified a distant icy object beyond Pluto that could become the latest addition to the solar system’s small group of recognised dwarf planets.
The object, named 2026 ED138, was discovered using the Vera C. Rubin Observatory in Chile. Researchers estimate that it measures between 600km and 1,500km in diameter and orbits approximately 46 times farther from the Sun than Earth.
By comparison, Pluto orbits the Sun at an average distance of about 40 times Earth’s distance from it.
However, further observations are needed to confirm whether 2026 ED138 qualifies as a dwarf planet.
If confirmed, it would join five dwarf planets currently recognised by the International Astronomical Union (IAU): Pluto, Eris, Haumea, Makemake and Ceres.
The first four orbit beyond Neptune, the solar system’s outermost planet, while Ceres is located in the main asteroid belt between Mars and Jupiter.
Based on current estimates, 2026 ED138 could rank among the largest known dwarf planets.
More Observations Needed To Confirm Its Size
Astrophysicist Matt Holman of the Center for Astrophysics, Harvard and Smithsonian, who first identified the object, said the discovery highlighted the potential for further breakthroughs using the Rubin Observatory and other telescopes.
To qualify as a dwarf planet, an object must have enough mass for its own gravity to pull it into a nearly round shape.
Current data suggest 2026 ED138 may meet this requirement, but scientists still need to establish its physical size and composition.
“The main thing we need to do is to establish the physical size of 2026 ED138,” Holman said.
Measuring the object presents a challenge because telescopes detect sunlight reflected from its surface. A smaller object with a highly reflective surface can appear just as bright as a larger object with a less reflective surface.
Holman said observations at longer wavelengths could help scientists determine its size by detecting the heat it emits.
One instrument that could assist is the Atacama Large Millimeter/submillimeter Array (ALMA), a powerful telescope facility also located in Chile.
A Frozen World In The Solar System’s Outer Reaches
The candidate lies in a frigid region beyond Neptune, where numerous icy objects orbit the Sun.
Pluto was once considered the solar system’s ninth planet before the IAU reclassified it as a dwarf planet in 2006 because it did not meet the organisation’s formal definition of a planet.
The discovery of 2026 ED138 could offer scientists another opportunity to study the distant objects that inhabit this largely unexplored region.
The finding was announced at a scientific meeting in Spokane, Washington, although researchers stressed that additional observations are required before its status can be confirmed.
