A large icy world orbiting beyond Pluto has been sitting in telescope images since at least 2016, and astronomers only just noticed it. The NSF–DOE Vera C. Rubin Observatory announced on Oct. 27 that it had found its first dwarf planet candidate, an object the International Astronomical Union's Minor Planet Center has provisionally designated 2026 ED138.

If follow-up measurements confirm its size and shape, ED138 would become only the sixth object formally recognized as a dwarf planet, joining Pluto, Ceres, Eris, Haumea and Makemake. Early estimates place its diameter between about 600 and 1,500 kilometers (370 to 930 miles). The top of that range would make it larger than Ceres, the smallest recognized dwarf planet at roughly 940 kilometers (585 miles) across.

For skywatchers and anyone who grew up memorizing the planets, the discovery is a reminder that the solar system's map is still being drawn — even in our own cosmic backyard. It also shows what a new generation of survey telescopes can find in data that older searches could not untangle.

Lost in the Crowd of the Milky Way

The most striking part of the story is where ED138 was hiding. The object sits in a region of sky close to the plane of the Milky Way, a field packed with millions of stars, according to the University of Washington. To most telescopes, the faint moving dot blended into the background, which is likely why it went undetected for so long.

Matthew Holman, a senior astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, told CNN that the object has spent the past two decades crossing the Milky Way from Earth's point of view. "People don't typically search for things in the Milky Way, because there's so many stars that it's really hard to find moving objects," Holman said in the report, published by WCPO.

Its position in the southern sky added another obstacle. Holman noted that many northern telescopes cannot easily observe that part of the sky, and fewer surveys search the south.

On the evening of Oct. 13, Holman ran Rubin data through a search code he developed with colleague Kevin Napier. The software compares billions of detections of moving objects to find those that belong to the same body. ED138 stood out because its brightness and distance pointed to an unusually large object.

Thirty Images Over Twenty Nights

To rule out an error, Holman passed the candidate to Mario Jurić, the Rubin Solar System lead scientist and a University of Washington astronomy professor. Jurić's search of Rubin's catalogs turned up 20 more observations. In all, Rubin's Simonyi Survey Telescope recorded ED138 30 times on 20 nights between March 4 and July 11, 2026, NOIRLab reported.

Archival images from the Dark Energy Camera on the Victor M. Blanco 4-meter Telescope in Chile, located through the Asteroid Institute's ADAM Precovery service, extended the record back to 2016. That gave the team more than 10 years of the object's orbit to work with. ED138 is currently about 46 astronomical units from the Sun, compared with Pluto's average distance of about 40.

The timing is notable. Many of those Rubin detections came during the observatory's commissioning phase, before it formally launched its 10-year Legacy Survey of Space and Time in July. That means the find arrived less than four months into the survey proper.

"Rubin Observatory's superpower is the ability to clearly capture movement and change among a vast number of objects and phenomena that humans have never seen before," said Edward Ajhar, the National Science Foundation'sprogram director for Rubin Observatory.

The Measurements Still Needed Before It Becomes Official

ED138 is a candidate, not a confirmed dwarf planet. Under the IAU's 2006 definition, a dwarf planet orbits the Sun, is massive enough for its own gravity to pull it into a nearly round shape, and has not cleared its orbit of similar objects. The size estimate rests on the object's distance, brightness and an assumed surface reflectivity, so the true diameter could fall anywhere in the wide current range.

"At this point, it's still a candidate. We really need to know how physically big it is, and that will take a few months, probably," Holman said.

Measuring that size likely requires infrared observations, which reveal how much heat the surface gives off and help pin down how reflective it is. A darker object at the same brightness would be larger, while a bright, icy one would be smaller. If ED138 sits near the low end of the range, it may still be round, but the case would be less certain.

An independent researcher not involved in the discovery called it significant. Michele Bannister, an associate professor at the University of Canterbury in New Zealand who studies small worlds of the solar system, said the object falls just within the range where scientists can begin to think of it as a world. She cautioned that, beyond its size, little is known about its physical characteristics.

If confirmed, ED138 would first receive a permanent number and then a name. Holman said people have already emailed suggestions, though the process for choosing a name is still unclear.

Science Value and the Search for More Hidden Worlds

The discovery is not a hazard to Earth and does not change anything about daily life. Its value is scientific. Large trans-Neptunian objects preserve clues about how the outer solar system formed, and ED138's orbit, reported to be tilted nearly 25 degrees, suggests gravitational interactions with Neptune pushed it off its original path.

The bigger story may be what comes next — more hidden worlds. Holman said there could be "a handful" more objects of ED138's size still undiscovered, and Rubin should eventually find them. Megan Schwamb, a Rubin Solar System team member at Queen's University Belfast, said she was surprised such an object turned up so early in commissioning.

Other observatories can now aim at ED138, and the Minor Planet Center will refine its orbit as observations accumulate. Readers can explore the orbit through Rubin's public Orbitviewer tool. ED138 is not visible to the naked eye, though Holman said very capable amateur astronomers could spot it with the right equipment if they know where to look.

The bottom line: a large icy body beyond Pluto has been confirmed as a real, distant object, but its status as a dwarf planet depends on size and shape measurements expected over the coming months.

What Readers Want to Know

What is 2026 ED138? It is a large icy object orbiting the Sun beyond Pluto, about 46 astronomical units away, identified in Rubin Observatory data and announced on Oct. 27, 2026.

Is ED138 officially a dwarf planet? Not yet. Astronomers must confirm that it is large enough to be pulled into a round shape by its own gravity before the IAU can recognize it.

How big is it? Current estimates range from about 600 to 1,500 kilometers (370 to 930 miles) across. The upper end would exceed Ceres, the smallest recognized dwarf planet.

Why wasn't it found earlier? It sits near the crowded plane of the Milky Way in the southern sky, where millions of background stars made it hard to pick out, and fewer telescopes search that region.

Can I see it from my backyard? Not with the naked eye. Holman said very capable amateur astronomers could detect it with the right equipment.

When will astronomers know more? Holman said measuring its true size will probably take a few months, likely with infrared observations.