Comparison of mid-infrared spectra of irradiated exoplanet atmospheres and brown dwarfs. In the left panel, we show JWST MIRI transit spectra from ∼ 4 to 12 μm for three giant exoplanets, inverted only as a comparative visual aid to the brown dwarf spectra on the right panel. Observational data (points) and associated best-fit retrieval models for the exoplanets are taken from D. Grant et al. (2023), D. Powell et al. (2024), and A. Dyrek et al. (2024; top to bottom, respectively). Equilibrium temperatures are noted, and molecular sources of opacity are labeled. In the right panel, we show MIR brown dwarf spectra from the Spitzer Space Telescope, adapted from G. Suárez & S. Metchev (2022). Effective temperatures and molecular absorption bands are labeled. Typical uncertainties on T_eff using J. Filippazzo et al. (2024) are approximately 1%–5%.