Scientists announced the possible discovery of a new dwarf‑planet candidate, designated 2026 ED138, orbiting the Sun well beyond Pluto’s average distance. The object, identified by the Vera C. Rubin Observatory’s survey instruments, appears unusually large and bright for a body in the remote outer Solar System.
How the object was detected
The find emerged from data collected during preparatory observations for the Rubin Observatory’s Legacy Survey of Space and Time (LSST), a ten‑year program that will repeatedly image the entire southern sky. On 13 October 2026, Matthew Holman, a Rubin Operations team member affiliated with the Center for Astrophysics | Harvard & Smithsonian, was reviewing those data. He employed a custom search code that compares billions of detections of moving objects, linking together observations that belong to the same source.
Holman’s analysis flagged a moving point of light that stood out for its brightness at a distance of roughly 46 astronomical units (AU) from the Sun—about six AU farther than Pluto’s average orbit of 40 AU. The object’s luminosity and estimated reflectivity led the team to calculate a diameter between 600 and 1,500 kilometres (370–930 miles), placing it among the largest known bodies in the trans‑Neptunian region.
“My first reaction was one of excited disbelief,” Holman said. “Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong.”
Characteristics and orbit
2026 ED138 is classified as a trans‑Neptunian object, meaning its orbit lies beyond Neptune. Its trajectory is tilted about 25 degrees relative to the ecliptic plane, a configuration astronomers label a “hot‑classical trans‑Neptunian object.” The inclination suggests the object’s original orbit may have been altered by past gravitational interactions with Neptune.
The dwarf‑planet candidate was located in a sky region close to the Milky Way’s galactic plane, an area densely populated with millions of stars. That crowding likely contributed to the object’s previous elusiveness, as most telescopes struggle to isolate faint, distant bodies against such a bright stellar backdrop. Continuous monitoring by the Rubin Observatory, combined with algorithms capable of sifting through millions to billions of light points, finally revealed the object’s presence.
Implications and next steps
If confirmed, 2026 ED138 would join a very small family of dwarf planets beyond Neptune, a group that currently includes Pluto, Haumea, Makemake, Eris and several others reclassified after the International Astronomical Union’s 2006 decision. A dwarf planet must be massive enough for its own gravity to shape it into a round form, a criterion that still requires verification for ED138.
Infrared observations are needed to refine the size estimate and to assess whether the object’s mass meets the dwarf‑planet threshold. “If confirmed as a dwarf planet, ED138 would join a very small family of worlds,” Holman noted, adding that the Rubin Observatory will continue imaging the southern sky throughout its ten‑year survey, potentially uncovering additional distant bodies that earlier surveys missed.
Edward Ajhar, NSF Program Director for the Rubin Observatory, highlighted the facility’s capability: “Rubin Observatory’s super power is the ability to clearly capture movement and change among a vast number of objects and phenomena that humans have never seen before. That power greatly extends our ability to reveal and understand new things about our Solar System, the Milky Way, and billions of other galaxies across the Universe.”
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