Astronomers have announced 2026 ED138, a large icy object in the Kuiper Belt estimated at roughly 600 to 1,500 kilometers (373 to 932 miles) across — potentially comparable in size to the dwarf planets Makemake and Haumea.

The discovery came from the Vera C. Rubin Observatory, whose 3.2-gigapixel camera can image an area of sky equivalent to about 40 full moons in a single exposure.

Astrophysicist Matthew Holman of the Harvard-Smithsonian Center for Astrophysics found the object on 13 October 2026 while analyzing Rubin data with software he developed with colleague Kevin Napier.

"My first reaction was one of excited disbelief," Holman said, adding that he immediately checked whether he or the code had done something wrong. The Minor Planet Center announced the object as a dwarf planet candidate on Wednesday, per Mashable.

If confirmed, it would become the sixth officially recognized dwarf planet, joining Ceres, Pluto, Haumea, Makemake and Eris.

The most striking part of the discovery is that ED138's entire orbit lies within Pluto's range of distances from the Sun — meaning it was hiding essentially in plain sight.

According to ScienceAlert, the object's orbit is tilted by about 24.5 degrees relative to the plane of the Solar System, a chaotic angle typical of trans-Neptunian objects that dramatically widens the sky astronomers must search.

Worse, BGR reports that the object sits against the crowded backdrop of the Milky Way, where thousands of bright stars camouflaged a faint, slow-moving sphere.

Objects this far out are also inherently hard to see: they reflect little sunlight, emit only a feeble thermal glow, and drift gradually against the background stars, so a telescope must be looking in the right place at the right time.

Mashable notes ED138 is actually bright enough that observers with fairly small telescopes could probably see it — yet nobody noticed it until Rubin's deep survey did.

The evidence trail is unusually rich. The team traced ED138 through 30 detections across 20 nights of Rubin observations from 4 March to 11 July 2026, according to ScienceAlert.

Then, using the Asteroid Institute's ADAM Precovery tool, Mashable reports the team found the object hiding in Dark Energy Camera archival images dating back to February 2016, with further captures in 2017, 2018, 2019 and 2023 — a ten-year observational record assembled in just days.

"Once we identify a new object, we can search back months, and sometimes even decades, finding it in images where nobody knew to look," said Mario Jurić, Rubin's lead solar system scientist at the University of Washington.

The combined data pinned down the orbit: the Minor Planet Center lists ED138 as taking about 281 years to circle the Sun, ranging from 36.86 astronomical units at perihelion to 49.04 at aphelion, slightly farther out on average than Pluto.

ED138 is a big deal precisely because of its scale: at up to roughly 1,500 kilometers wide, BGR reports it could be one of the largest objects ever found in trans-Neptunian space.

The exact size remains uncertain because a smaller, highly reflective icy world can appear as bright as a much larger dark one, so researchers cannot yet pin down the diameter without knowing its reflectivity, ScienceAlert explains.

Objects this size are likely massive enough for gravity to pull them into a roughly spherical shape — the defining trait of a dwarf planet — but confirmation requires infrared observations.

Beyond classification, the find matters scientifically: distant objects like ED138 are leftovers from the era when the planets formed, and its highly tilted orbit suggests ancient gravitational interactions flung it onto its strange path, making it a cosmic time capsule for the chaos that shaped the Solar System, per BGR.

ED138 is expected to be only the opening act.

Rubin saw first light in June 2025, and over the ten-year survey it began in June 2026, ScienceAlert reports it is expected to discover thousands of previously unknown objects in the outer Solar System, helping astronomers piece together its history and evolution — and perhaps even revealing worlds larger and stranger than anything found so far.

Among the tantalizing targets is the hypothetical Planet Nine, a massive undiscovered world proposed to explain the odd orbits of some distant objects; Rubin may finally settle whether those orbits point to a planet or, as ScienceAlert puts it, a swarm of rocks in a planet-shaped trenchcoat.

BGR reports astronomers may also point the James Webb Space Telescope at ED138 to learn more about it and check for a moon. "Any others hiding in the places earlier surveys skipped are now within reach," Holman said.