Original title: Combined JWST and HST Deep Imaging to Characterize the Smallest Known Trans-Neptunian Objects
Anastasia N. Morgan, Marielle R. Eduardo, David E. Trilling, Wesley C. Fraser +8 · September 2026
Beyond Neptune lies a ring of icy worlds called Trans-Neptunian Objects, or TNOs. Scientists want to know what these distant bodies are made of, but small ones are hard to see. To study them, researchers paired the James Webb Space Telescope with the Hubble Space Telescope. Webb spotted the faint, small objects in infrared light, while Hubble observed them in visible light at nearly the same time. Measuring how these bodies reflect different wavelengths reveals their surface colors. The team found that small cold classical TNOs share a narrow set of colors, matching the color sequence of much larger ones. Dynamically disturbed objects showed a wider mix of colors. Because small and large objects share the same patterns, their colors likely date back to when the solar system formed, rather than being altered by collisions over time.
You are organizing a bookshelf by color. You expect the thin books to have faded more over time than the thick ones. But when you line them up, the thin books are the same shade as the thick ones. In this paper, astronomers measured the colors of tiny and large Trans-Neptunian Objects and found they match, suggesting that billions of years of collisions have not altered the colors of smaller objects.
These findings help astronomers understand how the solar system formed. They show that the colors of these distant icy worlds, whether small or large, come from the same early processes, not from collisions breaking them apart later. This supports the idea that the building blocks of planets were already diverse in color at the very beginning.
The results are based on only thirteen TNOs from a single sky field, so they may not represent the entire population. The study focuses on two dynamical groups, excluding other types. The inference of a primordial origin relies on the absence of a size–color trend, which could be tested with larger samples.
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Combined JWST and HST Deep Imaging to Characterize the Smallest Known Trans-Neptunian Objects — Anastasia N. Morgan, Marielle R. Eduardo, David E. Trilling et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.