OUTER SOLAR SYSTEM • VERIFIED DISCOVERY • OCTOBER 28, 2026
2026 ED138: A Giant New Dwarf Planet Candidate Beyond Neptune
Status: Confirmed detection of a trans-Neptunian object; classification as a dwarf planet is provisional. Announced by the Minor Planet Center and Vera C. Rubin Observatory on October 27, 2026.
Discovery
Astronomer Matthew Holman identified 2026 ED138 on October 13 while searching Vera C. Rubin Observatory survey observations. Colleagues including Mario Jurić recovered additional observations. Rubin had recorded the object 30 times across 20 nights between March and July 2026; archival images from other telescopes extended the orbital record back to 2016.
What we know
- Distance: about 46 astronomical units from the Sun at discovery, beyond Neptune and farther out than Pluto's mean orbital distance.
- Estimated diameter: 600–1,500 kilometers, depending on surface reflectivity; approximately 1,000 km is a useful midpoint, not a measured diameter.
- Orbit: inclined roughly 25 degrees to the solar system's reference plane, placing it among dynamically excited “hot classical” trans-Neptunian objects.
- Discovery environment: near the crowded stellar background of the Milky Way, making detection by earlier searches difficult.
Why a candidate, not a confirmed dwarf planet?
The object is bright enough that its estimated size suggests self-gravity may have made it nearly round, an important dwarf-planet criterion. But reflected-light brightness depends on both size and albedo. Infrared observations are needed to better constrain its diameter and physical nature. It has not been formally recognized as a dwarf planet by the International Astronomical Union.
What can its orbit tell us?
The approximately 25-degree orbital tilt may reflect gravitational interactions during Neptune's migration and the early reshaping of the outer solar system. This is a scientific interpretation, not direct evidence of exactly where the object formed. Claims that ED138 originated outside the solar system or was captured from another star are speculative and not established by the discovery announcement.
Why MKP is following this
ED138 demonstrates how Rubin's repeated deep-sky observations and computational searches can uncover large, previously overlooked worlds. Future infrared measurements, light curves and continued tracking could refine its size, rotation, surface composition and dynamical history.
Primary sources
Vera C. Rubin Observatory: official discovery announcement, October 27, 2026
U.S. National Science Foundation: discovery report
Rubin Observatory: 3D orbit animation
Research explainer added October 28, 2026. Discovery confirmed; dwarf planet status and precise size remain uncertain.