A bright object beyond Pluto
Astronomers working with the NSF-DOE Vera C. Rubin Observatory in Chile have found a large, bright object in the outer solar system that may be a new dwarf planet. The object carries the provisional designation 2026 ED138 and sits beyond the orbit of Pluto on a tilted path around the sun. The International Astronomical Union's Minor Planet Center announced the finding.
Estimates put its diameter between 600 and 1,500 kilometres. That is wide enough for gravity to have pulled it into a roughly round shape, which is the main test that separates a dwarf planet from an ordinary asteroid.
How it stayed hidden for so long
The object was found in Rubin data collected between March 4 and July 11, 2026, by Matthew Holman of the Center for Astrophysics at Harvard and Smithsonian, who works on the observatory's software for spotting distant moving objects. Scientists had to pick the faint point out of a crowded field of stars, which is one reason it was not seen earlier. Rubin's 8.4-metre mirror and its very large digital camera make that kind of search possible.
The discovery came during the run-up to the Legacy Survey of Space and Time, the ten-year sky survey the observatory is built for. That survey is expected to find many more distant objects, including some far larger than the ones catalogued so far.
What confirmation would take
If confirmed, 2026 ED138 would rank among the largest objects found in the trans-Neptunian region. Only a handful of worlds are officially counted as dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake. Several other candidates are still being studied.
Confirmation requires more than size estimates. Astronomers need a precise orbit, a good measurement of brightness, and evidence that the body is in hydrostatic equilibrium. Rubin will keep tracking the object, and other telescopes will be asked to measure its colour and surface properties.
The outer solar system keeps producing surprises like this. Each new large body adds a data point to models of how the planets formed and how the early disk of ice and rock was scattered outward. For now, 2026 ED138 is a candidate, not a member of the club, but it is one of the strongest candidates found in years.