Astronomers have mapped the atmospheric weather of WISE 0855, the coldest known brown dwarf with a temperature of 265 K. Using the NIRSpec spectrograph on the James Webb Space Telescope, researchers captured time-resolved spectra over an 11-hour period with 15-minute intervals, marking a first for mid-infrared spectroscopy of such an object.
Data revealed significant fluctuations in carbon monoxide and phosphine, with CO brightness varying by up to 10%. Analysis suggests these variations are driven by a combination of temperature changes and shifting water cloud thickness. Models like PICASO and coolTLUSTY were used to interpret the complex, turbulent atmospheric dynamics observed by the telescope.
The study identified a discrepancy in vertical mixing rates, with turbulent diffusion coefficients for CO reaching 10^6 cm²/s compared to 10^1 cm²/s for phosphine. This suggests potential gaps in current chemical cycle models. Observations indicate the presence of jet streams rather than stable vortices, with potential rotation periods estimated between 5.4 and 5.6 hours.
These findings bridge the gap between weather patterns on gas giants like Jupiter and future atmospheric studies of Earth-like exoplanets. Future research will focus on longer observation series to better distinguish between rotation, zonal circulation, and large-scale atmospheric waves in the object's climate.
