Bright object beyond Pluto may be the solar system's sixth dwarf planet

The Vera C. Rubin Observatory has discovered what could be a new dwarf planet lurking beyond Neptune, potentially the sixth official dwarf planet in our solar system. This tiny world, designated 2026 ED138, is among the largest and brightest objects ever found past Neptune. If confirmed, ED138 would increase the number of recognized dwarf planets to six.

Matthew Holman, an astrophysicist at the Smithsonian Astrophysical Observatory and a member of the Rubin team, expressed excitement upon discovering the potential dwarf planet, stating that such objects are exceedingly rare. The hidden planet, designated 2026 ED138, orbits the sun at a distance roughly 46 times that of Earth's orbit. Its orbit is tilted at 25 degrees from the solar system plane, allowing it to blend in with the light from the Milky Way's bulge, making its detection challenging.

The formidable Vera C. Rubin Observatory, equipped with the largest digital camera ever built, scans the entire southern sky every few nights. This capability enables it to spot objects that move, including potential dwarf planets. Holman and his colleague Kevin Napier developed software algorithms to process the vast amounts of data collected by the observatory, which helped identify ED138.

By analyzing past data and archival images from the Dark Energy Camera mounted on the Victor M. Blanco 4-meter Telescope in Chile, the team mapped ED138's orbit over the past decade. The observatory, still in its initial phase of a 10-year mission, has already begun imaging the entirety of the southern sky.

If verified, ED138 would be classified as one of the largest and brightest objects discovered beyond Neptune. Its estimated diameter ranges from 370 to 930 miles (600 to 1,500 km), placing it above half the diameter of Pluto, the largest recognized dwarf planet. The discovery of ED138 brings astronomers closer to understanding the elusive dwarf planets in the outer reaches of our solar system.