Minor Planet Center publishes Rubin dwarf planet candidate’s orbit

The Minor Planet Center published observations and an orbit for 2026 ED138 on October 27, putting a new dwarf planet candidate from Vera C. Rubin Observatory into the public record. The U.S. National Science Foundation identifies it as an object beyond Pluto that other observatories can now study.

The object was found against the crowded star fields near the plane of the Milky Way. NSF’s account credits Rubin’s repeated observations and search algorithms with distinguishing its motion from the background stars. The agency’s article is an edited version of Rubin’s announcement.

Rubin dates the identification to October 13, when Matthew Holman of the Center for Astrophysics | Harvard & Smithsonian searched earlier observations using code developed with colleague Kevin Napier. The telescope had recorded ED138 30 times on 20 nights between March 4 and July 11, 2026.

Rubin’s team estimates its size at 600–1,500 kilometres from its brightness, distance and assumed surface reflectivity. That is an estimate, not a measured diameter. The observatory says infrared observations are needed to narrow the size and establish whether the object qualifies as a dwarf planet.

The circular includes archival observations dating to February 2016 alongside the 2026 Rubin measurements. Its orbital solution gives a period of about 281 years. Those records extend the observed arc well before the October identification and public announcement.

Rubin says scientists around the world can organise follow-up observations. Images on the Rubin Science Platform are available to Rubin data-rights holders; the public can explore the orbit through Orbitviewer. The candidate’s size and dwarf-planet status await further observations.