Study finds small trans-Neptunian objects keep record of their origins

By the Everything Space news desk · 16 Sep 2026 · written from the sources below

Image: Universe Today

New JWST and Hubble data show these distant icy bodies preserve surface color differences tied to where they formed, challenging assumptions about how much collisions erase such history.

Two new studies using data from the James Webb Space Telescope and Hubble have found that trans-Neptunian objects (TNOs), the icy bodies orbiting beyond Neptune, retain clues about their origins even at very small sizes.

TNOs fall into two broad categories: cold TNOs, which formed near their current far-flung orbits and tend to be reddish with circular, flat orbital paths, and hot TNOs, which formed closer in near the present orbits of Uranus and Neptune before being pushed outward during planetary migration. Hot TNOs show a wider range of colors and travel on more elliptical, tilted orbits.

Researchers had assumed that because small bodies are more easily flung around and battered by collisions than planets, their original surface compositions would likely be erased over time. The new research challenges that assumption, showing that the color distinctions between hot and cold TNOs hold true even among the smallest examples studied.

One study examined the surface colors and brightness of these objects, while a companion study looked at how TNOs are distributed by size. The size study found that hot and cold TNOs show similar size distributions, implying they have experienced comparable levels of collisional wear over their histories despite the different journeys that brought them to their current locations.

The findings suggest that the outward migration that carried hot TNOs to the far reaches of the solar system was not especially violent, since it did not scramble their surface characteristics beyond recognition.

The research also turned up fewer small TNOs than current models of planet formation predict, a discrepancy that may help explain why these objects have held onto their compositional history, while also raising new questions about how such small bodies formed in the first place.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.