Clara Sousa-Silva. Photo by Melanie Gonick
Bard College Assistant Professor of Physics Clara Sousa-Silva has published a new study, “The impending opacity challenge in exoplanet atmospheric characterization,” in the peer-reviewed journal Nature Astronomy. The paper is led by graduate student Prajwal Niraula (MIT), and coauthored by Julien de Wit (MIT), Iouli E Gordon (Harvard), Robert Hargreaves (Center for Astrophysics | Harvard & Smithsonian), Clara Sousa-Silva (Bard), and Roman Kochanov (Center for Astrophysics | Harvard & Smithsonian). Their research suggests that the current tools astronomers use to analyze data received from space telescopes may not be precise enough to accurately decode the unprecedented clarity of light-signals captured through next-generation observatories, including the extremely powerful James Webb Space Telescope (JWST) launched. by NASA in December 2021.
“We find ourselves in the extraordinary situation where the incredible engineering of JWST has resulted in the data collected from distant planets outcompeting our ability to interpret what we are seeing,” says Sousa-Silva.
Astronomers rely on ‘opacity models,’ which interpret how matter interacts with light, to describe and predict the physical properties of astronomical objects. This new study used existing opacity models to analyze spectral data collected from JWST and to look at the characterization of exoplanetary atmospheres—predicting atmospheric temperature, pressure, and elemental composition. The researchers warned that for each possible atmospheric signal from an exoplanet, multiple interpretations could be made with current models and fundamental molecular inputs. The imprecision from these models means that data from an alien atmosphere could be misinterpreted. The implications of such misinterpretations include our understanding of whether an exoplanet could support life or not.
“There is a scientifically significant difference between a compound like water being present at 5 percent versus 25 percent, which current models cannot differentiate,” says study coauthor Julien de Wit.
The authors show how the limits of our knowledge on light–matter interactions (ie opacity models) will affect our exploration of exoplanetary atmospheres. “Accounting for these limits will prevent biased claims,” they write. “Guided improvements in opacity models, their standardization and dissemination will ensure maximum return on investment from the next-generation observatories, including the James Webb Space Telescope.” Their findings call for an investment in improved laboratory and theoretical data on atmospheric molecules, and development of more precise opacity models.