Astronomers found a mysterious object beyond Neptune, and it could be a new dwarf planet

The powerful Vera Rubin Observatory has spotted what seems to be a dwarf planet circling the sun in the frigid depths beyond Neptune.

The icy object, known as 2026 ED138, is likely between 600 and 1500 kilometers (373 to 972 miles) wide, scientists say. It's therefore probably big enough to be sculpted into a sphere by its own gravity — a key characteristic that separates dwarf planets from asteroids and other small space rocks.

And if 2026 ED138 is indeed a dwarf planet, that's a pretty big deal, as astronomers have confirmed just five of them to date: Pluto, Ceres, Eris, Haumea and Makemake.

An illustration of the solar system showing the orbital pathway of newly discovered dwarf planet candidate 2026 ED138 (ED138).  (Image credit: NSF–DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA/R. ProctorImage Processing: M. Zamani (NSF NOIRLab)Orbit data provided by the IAU Minor Planet Center (MPCorb catalog), funded by NASA PDCO and the Tamkin Foundation.Star map: NASA/Goddard Space Flight Center Scientific Visualization Studio. Gaia DR2: ESA/Gaia/DPAC)

2026 ED138 was discovered by Matthew Holman, who works at the Center for Astrophysics | Harvard & Smithsonian (CfA). The big moment came on Oct. 13, when Holman was running previously collected Rubin data through a search code that he developed with his CfA colleague Kevin Napier.

That search revealed a mysterious object beyond Neptune's orbit. Despite its immense distance from the sun, this body was relatively bright, suggesting that it's larger than the average trans-Neptunian object.

"My first reaction was one of excited disbelief," Holman said in a statement on Tuesday (Oct. 27), the day the discovery of 2026 ED138 was announced. "Objects like this are very rare, so I immediately started checking whether I or the code had done something wrong."

Those checks involved a thorough search through Rubin's catalog. And that catalog is pretty heft, even though Rubin is a pretty new scope.

This image shows the orbital pathway of the newly discovered dwarf planet candidate 2026 ED138, as observed by the NSF-DOE Vera C. Rubin Observatory. This image is a composite of multiple images captured by Rubin between March 4 and July 11, 2026 at intervals indicated by the teal circles. ED138 is visible at the center of each circle. (Image credit: NSF-DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA. Acknowledgement: Image Processing: M. Jurić (UW), D. de Martin & M. Zamani (NSF NOIRLab))

The Vera Rubin Observatory sits atop Cerro Pachón, an 8,799-foot-tall (2,682 meters) mountain in northern Chile, and features a primary mirror 28 feet (8.4 m) wide. The scope achieved first light in April 2025 and began its main project, the 10-year-long Legacy Survey of Space and Time (LSST), in June of this year.

During the LSST, Rubin images the entire southern sky every few days using a 3.2-gigapixel camera, the largest digital camera ever built for astronomy. This work creates a high-resolution time-lapse "movie" that can reveal a great deal about the cosmos.

For example, astronomers think Rubin will shed light on dark energy and dark matter, the mysterious stuff that together makes up most of the universe's mass-energy budget. Its observations will also serve as a solar system inventory, helping scientists map out our cosmic backyard like never before. Rubin has already discovered more than 11,000 new asteroids, for example, with many more surely to come.

The LSST inventory will likely include a number of new dwarf planets as well — including, possibly, 2026 ED138. For the object definitely exists: Holman and his colleague Mario Jurić, who works at the University of Washington and serves as Rubin Solar System Lead Scientist, found that Rubin spotted 2026 ED138 30 separate times on 20 nights between March 4 and July 11 of this year.

And further digging revealed that the Dark Energy Camera (DEC), an instrument on the Víctor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in Chile, also spotted 2026 ED138. Indeed, DEC observations of the object go all the way back to 2016.

A mosaic of images captured by the NSF-DOE Vera C. Rubin Observatory of the newly discovered dwarf planet candidate 2026 ED138. Its distance from the sun places it beyond the orbit of Pluto, and initial analysis indicates that it may be among the largest and brightest bodies scientists have discovered in this region of the solar system. (Image credit: NSF-DOE Vera C. Rubin Observatory/NOIRLab/SLAC/AURA. Image Processing: M. Jurić (UW), D. de Martin & M. Zamani (NSF NOIRLab))

The data show that 2026 ED138's orbit is tilted by about 25 degrees relative to the plane of the solar system. It therefore likely had a gravitational interaction with Neptune, which knocked it off kilter, scientists say.

2026 ED138 currently lies about 46 astronomical units (AU) from the sun. (One AU is the Earth-sun distance — about 93 million miles, or 150 million kilometers). This puts it beyond Pluto's average distance from the sun, which is roughly 40 AU.

There is still much to learn about the object, however. For example, we won't know whether or not it's a dwarf planet until astronomers nail down its size. And that will require observations in infrared light, the range of wavelengths that NASA's James Webb Space Telescope is optimized for.

So stay tuned: There's doubtless more news about 2026 ED138 coming, and Rubin could turn up more worlds like it in the coming months and years.

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

Michael Wall is the Spaceflight and Tech Editor for Space.com and joined the team in 2010. He primarily covers human and robotic spaceflight, military space, and exoplanets, but has been known to dabble in the space art beat. His book about the search for alien life, "Out There," was published on Nov. 13, 2018. Before becoming a science writer, Michael worked as a herpetologist and wildlife biologist. He has a Ph.D. in evolutionary biology from the University of Sydney, Australia, a bachelor's degree from the University of Arizona, and a graduate certificate in science writing from the University of California, Santa Cruz. To find out what his latest project is, you can follow Michael on Twitter.