Brittany E. Miles, University of California, Santa Cruz
Beth A. Biller, University of Edinburgh, Institute for Astronomy
Polychronis Patapis, ETH Zürich
Kadin Worthen, Johns Hopkins University
Emily Rickman, European Space Agency - ESA
Kielan K.W. Hoch, Center for Astrophysics & Space Sciences
Andrew Skemer, University of California, Santa Cruz
Marshall D. Perrin, Space Telescope Science Institute
Niall Whiteford, American Museum of Natural History
Christine H. Chen, Johns Hopkins University
B. Sargent, Center for Astrophysics & Space Sciences
Sagnick Mukherjee, University of California, Santa Cruz
Caroline V. Morley, The University of Texas at Austin
Sarah E. Moran, The University of Arizona
Mickael Bonnefoy, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
Simon Petrus, Universidad de Valparaiso
Aarynn L. Carter, University of California, Santa Cruz
Elodie Choquet, Laboratoire d'Astrophysique de Marseille
Sasha Hinkley, University of Exeter
Kimberly Ward-Duong, Smith CollegeFollow
Jarron M. Leisenring, The University of Arizona
Maxwell A. Millar-Blanchaer, University of California, Santa Barbara
Laurent Pueyo, Space Telescope Science Institute
Shrishmoy Ray, University of Exeter
Steph Sallum, University of California, Irvine
Karl R. Stapelfeldt, California Institute of Technology
Jordan M. Stone, Naval Research Laboratory
Jason J. Wang, Northwestern University
Olivier Absil, Université de Liège
William O. Balmer, Johns Hopkins University
Anthony Boccaletti, L'Observatoire de Paris
Mariangela Bonavita, The Open University

Document Type


Publication Date


Publication Title

Astrophysical Journal Letters


We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a (∼8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color-magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST's NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20 μm at resolutions of ∼1000-3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion.









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Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


© 2023. The Author(s).


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