For years the Hubble Space Telescope has captured crisp spectral images of exoplanets transiting their host stars. Because those images include light filtered through the exoplanets’ atmospheres, they contain clues about atmospheric composition. (See the Quick Study by Heather Knutson, Physics Today, July 2013, page 64.) Absorption features in such spectra have produced evidence of water, carbon dioxide, methane, and even clouds in the atmospheres of extrasolar planets.

But Hubble’s workhorse detector for exoplanet atmosphere observations, the Wide Field Camera 3, collects light in only 13 wavelength bins. The James Webb Space Telescope, scheduled for a 2020 launch, will be able to resolve spectra into hundreds of bins. The abundance of data could yield far more detailed portraits of extrasolar atmospheres, but it also creates a challenge: how to decipher all that information.

Enter Kevin Heng and his coworkers at the University of Bern in Switzerland....

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