Astronomers may have discovered a new member of the Solar System’s dwarf planet family. The distant, icy object, provisionally designated 2026 ED138, was identified in data from the Vera C. Rubin Observatory in Chile.
If confirmed, it could become the sixth recognised dwarf planet, joining Pluto, Ceres, Eris, Haumea and Makemake.
Researchers estimate that 2026 ED138 measures between 600 and 1,500 kilometres (370 to 930 miles) across. It could rank among the largest trans-Neptunian objects (TNOs) discovered in the past two decades.
The object may also be larger than Ceres, currently the smallest recognised dwarf planet.
Object Orbits Beyond Pluto
The newly identified TNO orbits the Sun at approximately 46 astronomical units (AU). This places it farther away than Pluto, which has an average distance of around 40 AU from the Sun.
Matthew Holman, a senior astrophysicist at the Harvard and Smithsonian Center for Astrophysics, detected the object while analysing Rubin Observatory survey data using specialised software.
“My first reaction was one of excited disbelief,” Holman said.
His colleague, Mario Jurić, at the University of Washington, subsequently identified 20 additional observations dating back to March 2026. Researchers used these archived observations to reconstruct the object’s orbit over more than a decade.
Why Was the Object Not Discovered Earlier?
Despite its potential size, 2026 ED138 escaped detection in earlier surveys for several reasons.
The object lies in the southern hemisphere, a region that previous surveys did not cover as extensively. It is also located near the galactic plane, where millions of stars make it difficult to identify distant objects moving against the background.
The new discovery highlights how improved astronomical surveys can reveal objects that earlier observations missed.
Dwarf Planet Status Still Unconfirmed
However, astronomers have not yet confirmed whether 2026 ED138 qualifies as a dwarf planet.
To meet the classification criteria, an object must orbit the Sun, have enough mass for its own gravity to pull it into a nearly round shape, and not have cleared its orbital neighbourhood of other objects.
Further observations and analysis will help scientists determine whether 2026 ED138 meets these requirements.
Until then, the object remains a potential new addition to the Solar System’s dwarf planet family.
