Overview
- The James Webb Space Telescope NIRCam survey produced a definitive discovery of 27 ultra‑faint trans‑Neptunian objects, with results released as arXiv preprints and Astronomical Journal papers in early September 2026.
- The survey reached unprecedented faint limits, with a 40% detection threshold near m_F150W2 ≈ 28.8 and a faintest detection at m_F150W2 = 29.3, implying detections down to roughly 10 km assuming a 15% albedo over a 0.05 square‑degree field.
- Coordinated Hubble imaging recovered 13 of the JWST detections and produced optical–near‑IR colors and lightcurves that show the smallest cold classicals occupy the same color sequence as larger cold classical TNOs.
- Analyses find dynamically cold and hot subpopulations follow statistically consistent power‑law size distributions, a result that challenges models that predict different formation‑location size outcomes.
- The survey used a shift‑and‑stack search and machine‑learning vetting, combined with trailed‑PSF photometry and lightcurve analysis (including a contact‑binary candidate, 2015 GK56), and teams are proposing a larger JWST program to probe down to about 1 km to test planetesimal formation and collisional evolution models.