The impending opacity challenge in exoplanet atmospheric characterization
Abstract
With a new generation of observatories coming online this decade, the process of characterizing exoplanet atmospheres will need to be reinvented. Currently mostly on the instrumental side, characterization bottlenecks will soon appear at the models used to translate spectra into atmospheric properties. Limitations stemming from our stellar and atmospheric models have already been highlighted. Here, we show that the current limitations of the opacity models used to decode exoplanet spectra propagate into an accuracy wall at ~0.5-1.0 dex (that is, three- to tenfold) on the atmospheric properties, which is an order of magnitude above the precision targeted by James Webb Space Telescope Cycle 1 programmes and needed, for example, for meaningful C/O-ratio constraints and biosignature identification. We perform a sensitivity analysis using nine different opacity models and find that most of the retrievals produce harmonious fits owing to compensations in the form of >5σ biases on the derived atmospheric parameters translating into the aforementioned accuracy wall. We suggest a two-tier approach to alleviate this problem, involving a new retrieval procedure and guided improvements in opacity data, their standardization and optimal dissemination.
- Publication:
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Nature Astronomy
- Pub Date:
- November 2022
- DOI:
- 10.1038/s41550-022-01773-1
- arXiv:
- arXiv:2209.07464
- Bibcode:
- 2022NatAs...6.1287N
- Keywords:
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- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 16 Pages, 12 Figures