Overview
- Two linked papers published in The Astronomical Journal on Sept. 8 report that JWST’s NIRCam found 27 trans‑Neptunian objects (TNOs) and Hubble recovered 13 of them in follow‑up images.
- The team measured infrared brightness to infer sizes—some objects are estimated at roughly 6–10 km up to about 40 km—though those diameters depend on assumed surface reflectivity (albedo).
- The observed size distribution rises more slowly toward faint, small bodies than some planetesimal‑formation and collisional‑grinding models predict, meaning there are fewer tiny fragments than expected.
- Visible and near‑infrared colours show the smallest TNOs fall into the same ‘cold’ and ‘hot’ colour families as larger objects, which suggests their surfaces largely preserve original formation material.
- The result rests on a very narrow, ultra‑deep survey (0.05 square degrees) that used shift‑and‑stack image stacking plus machine‑learning vetting, and the authors stress short orbital arcs and small sky coverage leave sample size, orbit classification, and size inferences provisional as they plan expanded JWST programs to probe still smaller bodies.