Overview
- A Northwestern-led team published its analysis on June 18 reporting the first direct spectrum of GJ 504 b and concluding the data are best fit by models that include a deck of salt clouds.
- The spectrum was obtained with JWST’s NIRSpec in roughly two hours and extracted using new star‑subtraction and integral‑field angular differential imaging techniques to isolate the faint companion’s light.
- The data show clear molecular signatures including water vapor, carbon monoxide, methane, carbon dioxide, ammonia and hydrogen sulfide plus isotope-bearing CO and signs of disequilibrium chemistry.
- Salt clouds are an inferred, model‑dependent solution that mute deeper molecular features and help make retrieved atmospheric properties physically plausible, and the object’s mass and age uncertainties mean its formation as a planet or a brown dwarf remains unresolved.
- The study offers a testable observing and data‑processing approach for other cold, faint companions and signals that follow‑up spectroscopy and targeted observations will be needed to confirm cloud composition and pin down the object’s origin.