Rubin Observatory Spots 2026 ED138, a Possible New Dwarf Planet Orbiting Beyond Pluto

Our solar system may be about to gain a new dwarf planet. Astronomers working with data from the NSF–DOE Vera C. Rubin Observatory in Chile have identified a distant, icy body, provisionally named 2026 ED138, that orbits the sun beyond Pluto. If its size and shape are confirmed, it would join a very short list of officially recognized dwarf planets.

The discovery was announced on Tuesday, Oct. 27, at a press conference with Matthew Holman, a senior astrophysicist at the Center for Astrophysics | Harvard & Smithsonian, and Mario Jurić, a University of Washington astronomy professor who leads Rubin’s solar system team.

What is the new dwarf planet beyond Pluto?

2026 ED138 is a trans-Neptunian object, meaning it orbits the sun farther out than Neptune. According to UW News, it currently sits about 46 astronomical units (au) from the sun. One au is the average Earth-sun distance, roughly 93 million miles. For comparison, Pluto’s average distance is about 40 au.

Based on its distance, brightness and estimated surface reflectivity, the team puts its diameter somewhere between 600 and 1,500 kilometers (about 373 to 932 miles). Jurić described it as “roughly 1,000 kilometers across” and said it is “the largest trans-Neptunian object found in about 20 years.”

“Finding an object this big… is something that happens maybe once in a generation,” Jurić said, adding that Rubin found it “while we were still commissioning the telescope.”

Space.com reports that the object’s orbit is tilted by about 25 degrees relative to the plane of the solar system, which scientists say likely points to a past gravitational encounter with Neptune.

How was it found?

Holman spotted the object on the evening of Oct. 13 while running Rubin data collected earlier in 2026 through a search code he developed with colleague Kevin Napier. The code compares billions of detections of moving objects and links those that belong to the same body. The object stood out because it was unusually bright for its distance, a sign that it is large.

“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.”

Jurić then combed through Rubin’s catalogs and images and found additional observations going back to March 2026. Space.com reports Rubin captured the object 30 separate times on 20 nights between March 4 and July 11. The team also found it in archival images from the Dark Energy Camera on the Víctor M. Blanco Telescope going back to 2016, giving them more than ten years of its orbit to work with.

Why wasn’t it found earlier? The object lies in a part of the sky close to the plane of the Milky Way, crowded with millions of stars. UW News says it was likely lost among those background points of light until Rubin’s repeated scans and software picked it out.

Is it officially a dwarf planet yet?

No. 2026 ED138 is a candidate. To qualify as a dwarf planet, an object needs enough mass for its own gravity to pull it into a round shape. Icy bodies in the estimated size range are expected to be round, but the team says further observations are needed to pin down its exact size.

Space.com notes that measuring its size will require observations in infrared light, the wavelengths NASA’s James Webb Space Telescope is designed for. No timeline for those observations was given in the reports.

What are the possible dwarf planets in our solar system?

The International Astronomical Union currently recognizes five dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake. If confirmed, 2026 ED138 would become the sixth.

“If confirmed as a dwarf planet, ED138 would join a very small family of worlds,” Holman said.

Are there more planets beyond Neptune waiting to be found?

Rubin’s team clearly expects more discoveries. The observatory began its 10-year Legacy Survey of Space and Time (LSST) in June 2026, imaging the entire southern sky every few days with a 3.2-gigapixel camera, the largest digital camera ever built for astronomy.

In April, before the survey formally began, Rubin’s solar system team announced more than 11,000 new asteroids, including roughly 380 new trans-Neptunian objects. The team called that batch “the tip of the iceberg.”

“Rubin will image the whole southern sky again and again for 10 years, so any others hiding in the places earlier surveys skipped are now within reach,” Holman said.

Jurić added that once a new object is identified, astronomers can look back through months or even decades of older images to “precover” it, which speeds up how quickly they can work out its orbit.

The public can explore the object’s path in 3D through Rubin’s Orbitviewer web app.

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