Astronomers have found a new world hiding in our own solar system. It is an icy body orbiting far beyond Pluto, and it may be large enough to join the small, famous family of dwarf planets. The candidate is called 2026 ED138, and its discovery was announced on Tuesday, 28 October 2026, at a scientific meeting in Spokane, Washington.
This is not a confirmed dwarf planet yet. That word — candidate — matters, and the scientists behind the find are the first to say so. But even as a candidate, 2026 ED138 is remarkable: it is one of the largest objects ever found beyond Neptune, it was hiding in one of the brightest, most crowded parts of the sky, and it was found by a telescope still in its early days of work. If confirmed, it would become only the sixth recognised dwarf planet in our solar system.
What was found
The object was spotted using the Vera C. Rubin Observatory, a new telescope on the summit of Cerro Pachón in central Chile. Rubin is a joint project of the United States National Science Foundation and the Department of Energy, and it is built to photograph the whole southern sky again and again over ten years.
The discoverer is astrophysicist Matthew Holman of the Center for Astrophysics, Harvard and Smithsonian. Working with Kevin Napier, also of the Center for Astrophysics, Holman ran huge volumes of Rubin data through search software the team built to catch faint moving dots. When the software flagged 2026 ED138, Holman's first reaction, in his own words, was "excited disbelief". Objects this large are so rare, he said, that he immediately started checking whether he or the code had made a mistake.
Neither had. The team then found dozens of additional Rubin observations of the object from earlier in 2026, and older images from other instruments reaching back to 2016. Those earlier sightings — known as precoveries — helped map its orbit. Holman presented the find with Mario Jurić of the University of Washington, who leads Rubin's solar system science, at the annual meeting of the American Astronomical Society's Division for Planetary Sciences.
How big is it, and how far away?
Early estimates put 2026 ED138 somewhere between 600 and 1,500 kilometres across (roughly 370 to 930 miles). That is a wide range, and the reason for the uncertainty is simple and worth understanding: Rubin sees sunlight reflected from the object, not the object itself. A smaller, shinier world can reflect just as much light as a larger, darker one. Until astronomers measure the heat the object gives off, they cannot pin down its true size.
That is where another Chilean observatory comes in. By observing at longer wavelengths with ALMA, the Atacama Large Millimeter/submillimeter Array, astronomers can detect light emitted by the object itself rather than reflected sunlight, which helps measure its size. As Holman put it: "The main thing we need to do is to establish the physical size of 2026 ED138."
Even at the small end of the range, the object would be a major find. At the large end, it would rank among the largest dwarf planets known. For comparison, Pluto is about 2,377 kilometres across. Jurić called it roughly 1,000 kilometres across and "the largest trans-Neptunian object found in about 20 years", found while Rubin was still being commissioned.
Distance is easier to state. 2026 ED138 is currently about 46 times farther from the Sun than Earth is — 46 astronomical units, where one astronomical unit is the average Earth-Sun distance. Pluto, by comparison, is currently about 40 astronomical units from the Sun. The new object's orbit is also tilted about 25 degrees from the plane of the solar system, a tilt that may be the result of past gravitational nudges from Neptune.
Why did it stay hidden for so long?
This is one of the most surprising parts of the story. The object is bright enough, Holman said, that really capable amateur astronomers could see it. It was not hidden because it was too faint. It was hidden because of where it sits: in one of the brightest parts of the night sky, the band of the Milky Way, where countless stars crowd the view.
Finding a faint moving dot in that crowd is like spotting one person walking slowly through a packed stadium. Earlier surveys simply missed it among the stars. Rubin's software, designed to track faint moving objects across repeated images of the same sky, finally picked it out. As Holman said, the find shows that "we have not found all of the treasures in our solar system yet." Big discoveries are not always far away — sometimes they are waiting for someone to look at old data in a new way, as with England's new swamp dinosaur, Paludohadros proudlovii, which hid in a museum for 25 years.
What makes a world a dwarf planet?
The word "dwarf planet" is not just a label for a small planet. Under the International Astronomical Union's definition, a dwarf planet must orbit the Sun, must not be a moon of another body, must not have cleared its neighbourhood of other objects (that is the key difference from a full planet), and must have enough mass for its own gravity to pull it into a round shape.
That last point is why size matters so much for 2026 ED138. An icy body of standard composition at this size is expected to be round, because its own gravity would have overcome the strength of its material and pulled it into a sphere. That is why the team put it forward as a dwarf planet candidate. But "expected to be round" is not the same as "observed to be round", and confirmation will need better measurements of its size and shape.
If confirmed, 2026 ED138 would join just five recognised dwarf planets: Pluto, Eris, Haumea and Makemake, all of which orbit beyond Neptune, and Ceres, which sits in the main asteroid belt between Mars and Jupiter. Based on current data, the new candidate would be among the largest of the group.
Why the Rubin Observatory changes the game
Rubin is not just another big telescope. Its power comes from a combination of speed, depth and precision, as Jurić explained: it images the whole southern sky repeatedly, so it can spot faint moving objects and then look back through its own earlier images — and older images from other telescopes — to trace their orbits quickly.
That "precovery" ability is transforming how fast astronomers can understand a new object. In the past, a newly spotted distant body might take years of follow-up observations before its orbit was known well enough to say anything confident about it. With Rubin, the team could reach back to 2016 images in which the object had already been photographed, unnoticed, and start mapping its path almost immediately.
Telescopes keep surprising us this way. Earlier this month, another major observatory made its own first solar system discovery, as we reported in our story about Euclid's first comet, C/2026 S1, explained.
What happens next
Three things need to happen before 2026 ED138 can be called a dwarf planet with confidence.
First, astronomers need a better size measurement, most likely from ALMA or other infrared observations that detect the object's own heat. That will narrow the 600-to-1,500-kilometre range and confirm whether it is massive enough to be round.
Second, they need a better orbit. The precovery images back to 2016 are a strong start, but continued tracking will refine the orbit's shape and tilt, and how Neptune's gravity has shaped it over time. That orbital history may tell us where the object formed and how it ended up on such a tilted path.
Third, the International Astronomical Union must formally recognise it. The IAU's Minor Planet Center has already announced the provisional designation 2026 ED138, but dwarf planet status is a separate classification decision that will wait for the evidence above.
This is how astronomy normally works: a strong candidate is announced, the community checks it, and the classification follows the evidence. Readers should be wary of headlines that drop the word "candidate" — the careful version of this story is exciting enough on its own.
Why this discovery matters beyond one object
The outer solar system is still, in many ways, unmapped territory. The Kuiper Belt — the icy region past Neptune where 2026 ED138 lives — is a leftover construction site from the formation of the planets, full of frozen bodies that never grew into full planets. Every large object found there is a clue to how the solar system was built and how Neptune migrated outward long ago, scattering smaller bodies as it went.
A tilted orbit like that of 2026 ED138 is a particularly useful clue. Objects do not tilt themselves by 25 degrees for no reason. Something pushed it — most likely Neptune's gravity during the solar system's restless youth. Studying such objects is therefore a way of reading the solar system's early history, written in the orbits of its most distant survivors.
There is also a wider lesson about the pace of discovery. We sometimes talk as if the solar system were fully explored, a finished map with nothing left to add. The truth is the opposite: new worlds are still being found in our own backyard. If a world this big could hide in the Milky Way's glare until 2026, it is fair to ask what else is still out there. The same sense of surprise runs through other recent finds, including the Phoenix planet, a world reborn from a dead star.
What to watch for
Over the coming months, watch for three milestones: a size estimate from ALMA or another infrared observatory, which will decide whether the dwarf planet case strengthens or weakens; a refined orbit from the Minor Planet Center, built on the precovery images and new tracking; and, further down the road, any formal classification decision from the International Astronomical Union.
Until then, the honest summary is this: astronomers have found a large, icy world beyond Pluto, probably 600 to 1,500 kilometres across, orbiting about 46 times farther from the Sun than Earth on a tilted path, and it looks like a strong dwarf planet candidate. It is the largest distant object found in about two decades, found by a telescope that has barely begun its work, and it hints that more such worlds may be waiting in the star-crowded sky.
That is a big enough discovery on its own — no exaggeration needed.