Rubin Observatory Spots Candidate Dwarf Planet Beyond Neptune
Astronomers using the Vera C. Rubin Observatory have found 2026 ED138, an icy body beyond Neptune that may become the solar system's sixth dwarf planet.
The story in focus
Astronomers using the Vera C. Rubin Observatory in Chile have identified an icy object, 2026 ED138, orbiting beyond Neptune. Estimated at 600–1,500 km across, it may be a dwarf planet if further observations confirm it is round. The discovery was announced at a scientific meeting.
- 2026 ED138 orbits about 46 times farther from the sun than Earth, beyond Pluto's average distance.
- Its diameter is estimated between 600 and 1,500 kilometers.
- Confirmation as a dwarf planet requires establishing its physical size and roundness.
- If confirmed, it would join five IAU-recognized dwarf planets: Pluto, Eris, Haumea, Makemake, and Ceres.
Discovery and orbit
Astrophysicist Matt Holman of the Center for Astrophysics, Harvard & Smithsonian, first spotted 2026 ED138 using the Vera C. Rubin Observatory on Cerro Pachón in Chile. The telescope is a joint initiative of the US National Science Foundation and US Department of Energy.
The object orbits roughly 46 times farther from the sun than Earth, compared with Pluto's average of about 40 times. It is tilted about 25 degrees off the solar system's plane, an arrangement possibly linked to Neptune's gravitational pull, according to Scientific American. Archival sightings date back to 2016.
Size and confirmation steps
Initial measurements estimate a diameter between 600 and 1,500 kilometers, which would make it one of the largest dwarf planet candidates detected. However, size alone is not enough: a dwarf planet must have sufficient mass for its gravity to pull it into a round shape.
Holman said the main task is to establish the object's physical size. Because Rubin sees reflected sunlight, a smaller, more reflective object can appear as bright as a larger, darker one. Observations at longer wavelengths with the ALMA telescope in Chile could detect the object's own emitted light and help measure its size.
What is the next step to confirm 2026 ED138 as a dwarf planet?
Astronomers need further observations to determine its physical size and whether it is round. Longer-wavelength observations with ALMA could measure the object's own emitted light, helping establish its size.
Sources & further reading
- Possible new dwarf planet identified orbiting beyond Pluto ↗The Straits Times
- Astronomers may have just discovered our solar system’s sixth dwarf planet ↗Scientific American
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