Hubble and Webb Detect Fewer Small Trans‑Neptunian Objects Than Expected

Scientists have, for the first time, combined the observing power of NASA’s Hubble Space Telescope and the James Webb Space Telescope to probe the outermost reaches of the solar system, focusing on Trans‑Neptunian Objects (TNOs). These icy bodies orbit beyond Neptune and are key to understanding the early stages of planetary formation. The joint observations revealed a handful of the smallest and faintest TNOs ever seen directly, pushing the limits of both instruments.

The survey, which covered a wide swath of the Kuiper Belt, yielded an unexpected result: the population of small TNOs is significantly lower than theoretical models had predicted. By measuring the brightness and sizes of dozens of objects, the team found a sharp drop‑off in numbers for bodies less than a few kilometers across. This deficit suggests that collisional grinding or dynamical processes have removed or eroded many of the smallest bodies, challenging current assumptions about the size distribution and collisional history of the outer solar system.

The findings, announced by the research team, will prompt a re‑examination of models of planetesimal accretion and the long‑term evolution of the Kuiper Belt. The successful use of Hubble and Webb together also demonstrates a powerful new approach for studying distant, faint objects, opening the door to further investigations of the solar system’s most remote inhabitants.