A possible new dwarf planet found beyond Neptune: what we know about 2026 ED138
The new Vera C. Rubin Observatory has found 2026 ED138, a large icy world beyond Pluto that could become the sixth known dwarf planet in our solar system. Here's how it was found and what happens next.
Astronomers may have found a new dwarf planet in the far reaches of our solar system. The object, called 2026 ED138 (or “ED138” for short), orbits the Sun beyond Pluto, and it’s the first dwarf planet candidate discovered by the powerful new Vera C. Rubin Observatory.
The discovery was announced on October 27, 2026, by NOIRLab, the US national lab that helps run the observatory.
What is 2026 ED138?
- Where: about 46 AU from the Sun, meaning 46 times farther than Earth is from the Sun. Pluto’s average distance is about 40 AU.
- Size: estimated at 600 to 1,500 km wide (about 370 to 930 miles). For comparison, Pluto is about 2,377 km wide.
- Orbit: tilted about 25 degrees from the flat plane where most planets orbit. Scientists think Neptune’s gravity pushed it into this tilted path long ago.
- Type: a “trans-Neptunian object”, meaning an icy body orbiting beyond Neptune.
Could it really be a dwarf planet?
A dwarf planet is an object that orbits the Sun and is big enough for its own gravity to pull it into a round shape, but hasn’t cleared its orbit of other objects. Scientists expect icy bodies as big as ED138 to be round.
Right now, there are five officially recognized dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake. If ED138 is confirmed, it would become the sixth.
The uncertainty is in its size. Using normal light, astronomers can’t easily tell the difference between a small, shiny object and a large, dark one, since both can look equally bright. That’s why the size range is so wide.
How was it discovered?
- On October 13, 2026, astronomer Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian was searching Rubin Observatory data with a code he built with Kevin Napier. The code links faint, slow-moving dots across many images.
- He noticed one object that was unusually bright for its distance, a sign it might be big.
- Mario Jurić of the University of Washington then found more observations: Rubin had captured it 30 times on 20 nights between March and July 2026.
- The team also found it in old images from the Dark Energy Camera in Chile, going back to 2016. It had been there all along, but no one had spotted it.
It likely stayed hidden because it sits in a crowded part of the sky near the Milky Way, where it’s hard to pick out among countless stars.
“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.”
What is the Rubin Observatory?
The Vera C. Rubin Observatory in Chile has an 8.4-meter mirror and the largest digital camera ever built for astronomy (3.2 gigapixels). It began its 10-year survey of the sky, called the Legacy Survey of Space and Time, in June 2026, and has already found more than 11,000 new asteroids.
What happens next?
- Astronomers need infrared observations, possibly from the James Webb Space Telescope, to measure its true size. None are scheduled yet.
- Rubin will keep tracking it to refine its orbit.
- Becoming an official dwarf planet would need review by the International Astronomical Union (IAU).
- Scientists expect Rubin to find more dwarf planet candidates in the coming years.
Is this “Planet Nine”?
No. “Planet Nine” is a hypothetical large planet, several times bigger than Earth, that some scientists think may orbit far beyond Neptune. ED138 is much smaller than that. But Rubin’s deep sky survey is one of the best tools for testing whether Planet Nine exists, so discoveries like this show the search is getting more powerful.
Frequently asked questions
What is 2026 ED138?
A large, icy object beyond Pluto discovered by the Rubin Observatory, and a candidate to become the sixth known dwarf planet.
How big is 2026 ED138?
Between about 600 and 1,500 km wide. Infrared observations are needed to narrow this down.
How many dwarf planets are there?
Five are officially recognized: Pluto, Ceres, Eris, Haumea and Makemake. ED138 could become the sixth.
Who discovered 2026 ED138?
Matthew Holman found it on October 13, 2026, in Rubin Observatory data, working with Mario Jurić and others.
Can I see it with a telescope?
No. It’s extremely faint and far away, so it needs very large professional telescopes. You can explore its orbit online through Rubin’s Orbitviewer app.
Sources
- NSF–DOE Vera C. Rubin Observatory reveals its first dwarf planet candidate (NOIRLab)
- Rubin Observatory reveals its first dwarf planet candidate (SLAC)
- Astronomers found a mysterious object beyond Neptune, and it could be a new dwarf planet (Space.com)
- ED138 dwarf planet candidate beyond Pluto (CNN)
- Possible sixth dwarf planet was hiding in decade-old data (Tech Times)
