Overview
- A moving source in Vera C. Rubin Observatory data was flagged by Matthew Holman on Oct. 13 and the discovery was presented publicly and listed by the IAU Minor Planet Center on Oct. 27.
- Preliminary orbit fits place 2026 ED138 about 46 astronomical units from the Sun and its optical brightness implies a diameter between roughly 600 and 1,500 kilometers depending on surface reflectivity.
- Researchers found the object in Rubin images from March–July 2026 and traced it in archival Dark Energy Camera data from 2016 plus Palomar photographic plates from 1954, which lengthen its orbital arc and improve occultation predictions.
- Teams of professional and amateur observers organized an occultation campaign (including a Halloween attempt) and plan thermal and infrared follow up with facilities such as JWST and ALMA to measure true size, shape and any moons.
- If follow-up shows ED138 is in hydrostatic equilibrium (round), it would meet IAU criteria to be classified as a dwarf planet and join the five known now, and the find highlights Rubin’s early power to reveal large, previously missed outer‑solar‑system bodies.