Hubble and Webb Together Spot 27 New Tiny Trans‑Neptunian Objects

NASA’s Hubble and James Webb telescopes jointly surveyed a patch of sky beyond Neptune, revealing 27 previously unseen trans‑Neptunian objects (TNOs). The faintest of these has a diameter of only about 3 miles (5 km), a size that ground‑based telescopes cannot detect. Contrary to expectations, the survey found fewer small TNOs than planet‑formation models predict. Color measurements show that the smallest bodies share the same surface hues as larger TNOs, suggesting that collisions have not significantly altered their surfaces. Size‑distribution analysis indicates that both dynamically cold and hot populations exhibit similar patterns, implying that planetesimal formation produced comparable size ranges regardless of the disk’s temperature or density. These observations refine our understanding of the early solar‑system environment and the processes that built the building blocks of planets.