When it comes to studying alien worlds, the James Webb Space Telescope could be drastically wrong, though through no fault of its own.
That’s the finding of a new study by researchers who looked not at the Webb Telescope’s optics, but at the models scientists use to interpret findings after the telescope has made an observation.
Specifically, the models scientists use to understand opacity, the ease with which light passes through an atmosphere, aren’t accurate enough, according to MIT graduate student Prajwal Niraula, co-author of a new paper published on Thursday at Astronomy of nature. And because Webb studies exoplanets (planets around stars other than our Sun) by measuring the wavelengths of light that pass through a planet’s atmosphere using its spectroscopy instrument, the less accurate models could mean that the observations of the Webb telescope are off reality by an order of magnitude.
“Currently, the model we use to decipher the spectral information is not up to the accuracy and quality of the data we have from the James Webb telescope,” Niraula said in a press release. “We need to up our game and tackle the problem of opacity together.”
Webb’s spectrometer instrument obtains a “spectrum,” a collection of wavelengths of light shining through an exoplanet’s atmosphere. Because different molecules absorb light at different wavelengths, the unique pattern of a spectrum can tell scientists which compounds are present in what amounts in a planet’s atmosphere, including gases and organics that might indicate signs of biological activity.
So failing to solve the opacity model problem could, in practice, mean that scientists miss signs of life on an exoplanet or get a false positive for possible signs of alien life in an exoplanet atmosphere.
“There is a scientifically significant difference between a compound like water present at 5% versus 25%, which current models cannot differentiate,” Julien de Wit, assistant professor in the Department of Earth, Atmospheric and Planetary Sciences from MIT and co-authored a study, he said in a press release.
In their study, the researchers created alternative opacity models that altered certain assumptions about how light and matter would interact in an exoplanet atmosphere. They then fed Webb’s spectra through these models and each produced very different results from each other, but also that each model seemed to fit the data very well; it would be difficult for scientists looking at these data to know they were wrong, that is, unless they knew what to look for.
“We found that there are enough parameters to adjust, even with a wrong model, to get a good fit, meaning you wouldn’t know your model is wrong and what it’s telling you is wrong,” said Dr. of Wit.
The researchers suggest several ways in which opacity models could be improved to match the accuracy of Webb’s optics, starting with more laboratory experiments with ground models, model refinement, and a central database with a standardized format for help astronomers update their models based on spectral data and experiments.
“There’s a lot that could be done if we knew exactly how light and matter interact,” Niraula said. “We know enough about the conditions on Earth, but as soon as we move into different kinds of atmospheres, things change, and that’s a lot of data, with increasing quality, that we risk misinterpreting.”
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