The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems VIII: Patchy Forsterite and Enstatite Clouds in the Atmosphere of VHS 1256 b.

[astro-ph.EP] JWST defines a new era for the data-driven approach of retrieval modelling, which has become a cornerstone tool for the statistical inference of exoplanetary and brown dwarf properties.

The Early Release Science program #1386 observations of VHS 1256 b represent a huge jump in data quality, data quantity and spectral coverage for such objects. VHS 1256 b is a young, planetary mass and extremely variable companion that populates the enigmatic L/T cohort of substellar atmospheres.

In this first retrieval analysis of the full 1 – 18 micron dataset, we apply the Brewster retrieval framework to the NIRSpec and MIRI spectroscopic observations of VHS 1256 b, exploring a variety of cloud species and structures. Using Delta(BIC) we find that the data is best described by a forsterite (Mg2SiO4) and enstatite (MgSiO3) cloud combination. Our analysis shows a strong preference for patchy silicate cloud coverage, which aligns with VHS 1256 b’s extensive and well documented spectral variability.

Our retrieval is able to place constraints on the abundances of H2O, CO, CO2, CH4 as well as NH3. We also show that the retrieved parameters are sensitive to the data used and the relative signal-to-noise ratios between data from different instruments. We conclude with the next steps for the wider retrieval community to better understand young and cloudy exoplanetary atmospheres.

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems VIII: Patchy Forsterite and Enstatite Clouds in the Atmosphere of VHS 1256 b, Retrieval Lessons Learned and Outlook to the Future

Niall Whiteford, Jacqueline K. Faherty, Ben Burningham, Johanna M. Vos, Simon Petrus, Polychronis Patapis, Beth A. Biller, Andrew Skemer, Sasha Hinkley, Emily Calamari, Genaro Suárez, Kelle L. Cruz, Brittany E. Miles, Aarynn L. Carter, Francisco A. Martinez, Melanie J. Rowland, Olivier Absil, Arthur D. Adams, William O. Balmer, Anthony Boccaletti, Mariangela Bonavita, Mickaël Bonnefoy, Mark Booth, Brendan P. Bowler, Zackery W. Briesemeister, Marta L. Bryan, Per Calissendorff, Faustine Cantalloube, Benjamin Charnay, Gaël Chauvin, Christine H. Chen, Elodie Choquet, Valentin Christiaens, Gabriele Cugno, Thayne Currie, Camilla Danielski, Matthew De Furio, Trent J. Dupuy, Samuel M. Factor, Michael P. Fitzgerald, Jonathan J. Fortney, Kyle Franson, Julien H. Girard, Eileen C. Gonzales, Carol A. Grady, Thomas Henning, Dean C. Hines, Callie E. Hood, Kielan K. W. Hoch, Alex R. Howe, Markus Janson, Paul Kalas, Jens Kammerer, Grant M. Kennedy, Pierre Kervella, Minjae Kim, Daniel Kitzmann, Adam L. Kraus, Masayuki Kuzuhara, Pierre-Olivier Lagage, Anne-Marie Lagrange, Kellen Lawson, Cecilia Lazzoni, Jarron M. Leisenring, Ben W. P. Lew, Michael C. Liu, Pengyu Liu, Jorge Llop-Sayson, James P. Lloyd, Anna Lueber, Bruce Macintosh, Mathilde Mâlin, Elena Manjavacas, Sebastián Marino, Mark S. Marley, Christian Marois, Raquel A. Martinez, Elisabeth C. Matthews, Brenda C. Matthews, Dimitri Mawet, Johan Mazoyer, Michael W. McElwain, Stanimir Metchev, Michael R. Meyer, Maxwell A. Millar-Blanchaer, Paul Mollière, Sarah E. Moran, Caroline V. Morley, Sagnick Mukherjee, Paulina Palma-Bifani, Eric Pantin, Marshall D. Perrin, Laurent Pueyo, Sascha P. Quanz, Andreas Quirrenbach, Shrishmoy Ray, Isabel Rebollido, Jea Adams Redai, Bin B. Ren, Emily Rickman et al. (26 additional authors not shown)

Comments: Accepted for publication in ApJL. 28 Pages. 12 Figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2608.06583 [astro-ph.EP] (or arXiv:2608.06583v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2608.06583
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Submission history
From: Niall Whiteford
[v1] Thu, 6 Aug 2026 20:53:19 UTC (13,191 KB)
https://arxiv.org/abs/2608.06583

Astrobiology, Astrogeology, Exoplanet,