Move over Pluto! Scientists spot huge new dwarf planet candidate lurking beyond edge of solar system

Move over Pluto – there's a new potential heavyweight in our solar system, and scientists believe it could be one of the biggest dwarf planet candidates ever discovered.

Astronomers using the powerful Vera C. Rubin Observatory in Chile have spotted a mysterious object lurking beyond Pluto, raising the prospect of a new addition to the dwarf planet family. The object, provisionally named ED138 by the International Astronomical Union's Minor Planet Center, is still awaiting further observations to confirm its nature and size. If the preliminary findings are verified, it could join the five recognised dwarf planets: Pluto, Ceres, Eris, Haumea and Makemake.

So why has it taken so long to spot something potentially so significant?

ED138 was found in a crowded patch of sky close to the plane of the Milky Way, where millions of stars make it notoriously difficult to pick out distant objects. But Rubin Observatory's extraordinary technology gave scientists a crucial advantage. Located in Chile, the observatory boasts the largest digital camera ever built and is designed to repeatedly scan the sky, capturing subtle changes and movement that might otherwise go unnoticed.

By comparing observations and using powerful data-processing algorithms, researchers were able to identify ED138 moving against the dazzling background of stars. Edward Ajhar, National Science Foundation programme director for Rubin Observatory, said the facility's ability to capture movement among huge numbers of objects opened up exciting new possibilities.

Its discoveries could help scientists better understand everything from our own solar system to the Milky Way and distant galaxies. ED138 is just one of the many solar system objects spotted by the observatory this year. In April, Rubin submitted observations of more than 11,000 new asteroids.

Kathy Turner, Department of Energy programme manager for Rubin Observatory, said its unique capabilities made it an incredible tool for investigating a wide range of astronomical phenomena. But before ED138 can claim a place alongside Pluto, astronomers will need to conduct follow-up observations to establish more about its size, orbit and physical characteristics.

Pluto itself was reclassified as a dwarf planet in 2006. Under International Astronomical Union rules, a planet must orbit the Sun, be nearly round and have cleared its orbital neighbourhood. Dwarf planets meet the first two conditions but not the third.

For now, ED138 remains a candidate – but its discovery offers another tantalising glimpse of the secrets waiting to be uncovered in the distant reaches of our cosmic backyard.