Once-in-a-Generation Find: a Friend for Pluto

Don't feel bad for Pluto out there on the cold edge of our solar system: new observations show it has a friend. Astronomers say a hefty object spotted about 4.3 billion miles from the sun is likely a new dwarf planet, temporarily tagged 2026 ED138. It was flagged by software combing images from the Vera C. Rubin Observatory in Chile, which has already discovered some 2,300 objects beyond Pluto, boosting the known population beyond that dwarf planet by roughly half, reports the New York Times. ED138—currently separated from Pluto by about six times the average distance between Earth and the Sun—is the largest of those finds, somewhere between about 370 and 930 miles wide.

"Finding an object this big ... is something that happens maybe once in a generation," Mario Juric of Rubin's solar system team says in a release. "It's the largest trans-Neptunian object found in about 20 years." As of now, the International Astronomical Union recognizes only five dwarf planets—Pluto (more than 1,400 miles wide), Ceres, Eris, Haumea, and Makemake—though many more are considered possible candidates. ED138 "would rank around the 20th largest among dwarf planets and dwarf planet candidates," the Times reports. Future observations, possibly including NASA's James Webb Space Telescope, could confirm its status and reveal whether it has a moon, an atmosphere, or both.