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Arxiv: The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b Published: 9/1/2022 8:33:18 PM Updated: 7/4/2024 7:23:33 AM

Paper abstract: We present the highest fidelity spectrum to date of a planetary-mass object.VHS 1256 b is a <20 M_\mathrm{Jup} widely separated (~8\arcsec, a =150 au), young, planetary-mass companion that shares photometric colors andspectroscopic features with the directly imaged exoplanets HR 8799 c, d, and e.As an L-to-T transition object, VHS 1256 b exists along the region of thecolor-magnitude diagram where substellar atmospheres transition from cloudy toclear. We observed VHS 1256~b with \textit{JWST}'s NIRSpec IFU and MIRI MRSmodes for coverage from 1 \mum to 20 \mum at resolutions of ~1,000 -3,700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassiumare observed in several portions of the \textit{JWST} spectrum based oncomparisons from template brown dwarf spectra, molecular opacities, andatmospheric models. The spectral shape of VHS 1256 b is influenced bydisequilibrium chemistry and clouds. We directly detect silicate clouds, thefirst such detection reported for a planetary-mass companion.