Possible Sixth Dwarf Planet Spotted Beyond Neptune by New Rubin Observatory
Named 2026 ED138, the icy world could be up to 1,500 km across and orbits farther out than Pluto.
Astronomers may have found a new dwarf planet in the outer reaches of our solar system. The object, catalogued as 2026 ED138, was picked out in data from the Vera C. Rubin Observatory in Chile and, if confirmed, would become only the sixth known dwarf planet after Pluto, Ceres, Eris, Haumea and Makemake.
What we know
ED138 lies about 46 astronomical units from the Sun, beyond Pluto’s average distance of around 40 AU. Based on its brightness, scientists estimate it is between 600 and 1,500 km wide, large enough that its own gravity could have pulled it into a round shape, one of the key tests for dwarf planet status.
Its orbit is tilted by roughly 25 degrees to the plane in which the planets travel. Researchers believe a gravitational encounter with Neptune long ago knocked it onto this inclined path.
How it was found
Matthew Holman of the Center for Astrophysics, Harvard and Smithsonian, spotted the object on 13 October while combing through Rubin data with software he built with Kevin Napier. The telescope had recorded it 30 times across 20 nights between March and July this year. Older images from the Dark Energy Camera, going back to 2016, helped confirm the orbit. The find was announced on 27 October.
Holman described his first reaction as “excited disbelief” and said he immediately rechecked his work because such objects are so rare.
What next
Infrared observations, possibly from the James Webb Space Telescope, are needed to measure ED138’s size accurately before it can be formally classed as a dwarf planet. Rubin’s ten-year Legacy Survey of Space and Time, which began in June 2026 and photographs the southern sky every few nights, is expected to uncover many more such distant worlds.
Featured image: Hubble photomap of Pluto, the best-known dwarf planet beyond Neptune. Photo: NASA, ESA, and M. Buie (Southwest Research Institute), Wikimedia Commons, Public domain (source).
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