The Campus Review
October 28, 2026
The Vera C. Rubin Observatory has discovered a new dwarf planet candidate named 2026 ED138 beyond Pluto. Astronomers found it in observations collected between March 4 and July 11, 2026.
The object is about 46 astronomical units (AU) from the Sun, farther away than Pluto on average. Scientists estimate that it is 600 to 1,500 kilometers wide. More observations are needed to determine whether it qualifies as a dwarf planet.
Key Facts About 2026 ED138
| Feature | Details |
| Object name | 2026 ED138 |
| Classification | Dwarf planet candidate and hot-classical trans-Neptunian object |
| Observatory | Vera C. Rubin Observatory, Chile |
| Astronomer who identified it | Matthew Holman |
| Observation period | March 4 to July 11, 2026 |
| Number of observation nights | 20 |
| Distance from the Sun | About 46 AU |
| Estimated diameter | 600-1,500 km |
| Orbital tilt | Nearly 25 degrees |
How Rubin Observatory Found the New Dwarf Planet Candidate
Astronomer Matthew Holman identified 2026 ED138 while using search software to study earlier data from the Rubin Observatory.
The Rubin Observatory is located on Cerro Pachón in Chile. It has an 8.4-meter telescope and a 3,200-megapixel camera that repeatedly scans the southern sky.
The object may have escaped earlier searches because it lies near the plane of the Milky Way. This region contains millions of stars, making faint objects difficult to spot.
Rubin’s software compares billions of detections from different observations. This helps astronomers identify moving objects that might otherwise go unnoticed.
Holman described his reaction in the official announcement:
“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 Scientists Know About 2026 ED138
Scientists have identified several important details about the new dwarf planet candidate.
- Estimated size: Its diameter may be between 600 and 1,500 kilometers. The exact size depends partly on how much sunlight its surface reflects.
- Possible shape: Icy objects of this size are expected to be round because of their own gravity. Further observations are needed to learn more about its physical properties.
- Tilted orbit: 2026 ED138 is a hot-classical trans-Neptunian object. Its orbit is tilted nearly 25 degrees relative to the main plane of the Solar System.
- Location: It belongs to the group of objects that orbit the Sun beyond Neptune.
How Older Images Helped Track Its Orbit
After finding 2026 ED138, researchers searched older astronomical images to learn more about its path.
The Asteroid Institute’s ADAM Precovery service helped researchers find the object in archived images taken by the Dark Energy Camera (DECam). These images extend the observation record back to 2016, helping scientists track its orbit over more than a decade.
Mario Jurić, a member of Rubin’s Solar System team and an astronomer at the University of Washington, explained why this matters:
“Rubin is giving us an unprecedented capacity to explore the sky through a combination of speed, depth, and precision.”
He also explained that researchers can search older images after finding a new object. This process, known as precovery, helps scientists calculate an object’s orbit more accurately.
Why the Discovery Matters
The outer Solar System contains icy objects left over from the early stages of planetary formation. Studying them can help scientists understand how our Solar System developed.
The discovery of 2026 ED138 matters for two main reasons:
- Finding overlooked objects: The discovery shows that large objects can remain hidden in crowded parts of the sky.
- Improving future searches: Rubin Observatory will repeatedly scan the southern sky over its planned ten-year survey, helping astronomers find and track more distant objects.
Holman highlighted the possibility of future discoveries:
“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 ten years, so any others hiding in the places earlier surveys skipped are now within reach.”
What Happens Next?
Scientists need more observations to determine whether 2026 ED138 qualifies as a dwarf planet. Infrared observations can help them estimate its size more accurately because visible brightness alone cannot show whether an object is small and reflective or larger and darker.
For now, 2026 ED138 remains a new dwarf planet candidate, not a confirmed dwarf planet. Its discovery offers an early look at how Rubin Observatory’s long-term survey could reveal more dwarf planets beyond Pluto.
After the Japan-led Phobos sample-return mission, the discovery of 2026 ED138 is another exciting development in space exploration, offering a new opportunity to study the distant reaches of our Solar System.
Pranjal Kharche
