The Vera C. Rubin Observatory has identified 2026 ED138, a large object beyond Pluto that could qualify as a dwarf planet. Observations stretching back to 2016 establish its orbit, while its estimated size still depends on uncertain surface reflectivity. Infrared follow-up is needed to narrow that range and confirm its classification.
Science··Midday
A distant object emerges from Rubin’s images
The Vera C. Rubin Observatory, a sky-survey telescope in Chile, has identified 2026 ED138 as a dwarf-planet candidate beyond Pluto.[1], [2]
ED138 is about 46 astronomical units from the Sun; one astronomical unit is the average Earth–Sun distance. Pluto’s average distance is about 40 astronomical units. The discovery was announced on 27 October, with the classification still provisional.[1]
Astrophysicist Matthew Holman found the candidate on 13 October while searching early Rubin data with software developed alongside Kevin Napier. The software connects detections of moving objects across observations. Astronomer Mario Jurić then searched the telescope’s catalogues and images for additional appearances, recovering earlier appearances of the same body.[1]
Archival observations extend the orbit to 2016
Rubin had recorded ED138 30 times across 20 nights between 4 March and 11 July. Older images from the Dark Energy Camera, an astronomical imaging instrument, show the body as early as 2016. Together, the observations trace more than 10 years of its orbit. Its path is tilted nearly 25 degrees from the Solar System’s plane. Researchers suggest past gravitational interactions with Neptune as a possible explanation for that inclination.[1]
Size and shape await infrared follow-up
Distance and brightness, combined with assumed surface reflectivity, put the estimated diameter between 600 and 1500 km. That range depends on how much sunlight the surface reflects. Infrared observations are needed to constrain the size and confirm whether ED138 meets the dwarf-planet classification, which requires enough mass for gravity to make the object round.[1]
ED138 appeared against the crowded star field near the Milky Way’s plane, a setting that may have concealed it from earlier searches. Rubin repeatedly monitors the southern sky and links moving points among those background stars. The object’s images are available to researchers with Rubin data rights, while the public Orbitviewer tool displays its orbit.[1]
The International Astronomical Union currently recognizes five dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake. ED138’s status remains a candidate pending follow-up. The discovery observations were also released through the Minor Planet Center, the international body that collects observations of small Solar System objects.[1]
