Tuesday, September 27, 2022

NASA’s Webb telescope could be drastically wrong, experts say

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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 according to a new study by researchers who didn’t look at the optics of the Webb telescope, but at the models scientists use to interpret the results after the telescope makes an observation.

In particular, the models scientists use to understand opacity, how easily light passes through an atmosphere, are not accurate enough, according to MIT graduate student Prajwal Niraula, a co-author of a new paper published in Thursday natural astronomy. And since Webb studies exoplanets — planets around stars other than our Sun — by measuring the wavelengths of light that penetrates a planet’s atmosphere with his spectroscopy instrument, the less accurate models could mean that the Webb telescope’s observations are down by an order of magnitude deviate from reality.

“Currently, the model we are using to decode spectral information does not match the accuracy and quality of the data we have from the James Webb Telescope,” Niraula said in a press statement. “We need to up our game and tackle the opacity issue 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, a spectrum’s unique pattern can tell scientists what compounds are present in a planet’s atmosphere and in what amounts, including gases and organic matter that could indicate signs of biological activity.

If the opacity model problem is not solved in practice, it could mean that scientists miss signs of life on an exoplanet or get a false positive for potential signs of extraterrestrial life in an exoplanet atmosphere.

“There’s a scientifically significant difference between a compound like water being 5 percent versus 25 percent present that current models can’t distinguish,” Julien de Wit, an assistant professor in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, and a fellow student. Author said in a press statement.

In their study, the researchers created alternative opacity models that changed certain assumptions about how light and matter would interact in an exoplanet atmosphere. Then they fed Webb 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; In other words, it would be difficult for scientists looking at this data to know it was wrong unless they knew what to look for.

“We found that there are enough parameters that one can tweak, even with the wrong model, to still get a good fit, meaning you wouldn’t know your model was wrong and what it was telling you , is wrong,” said Dr. de Wit.

The researchers suggest several ways that opacity models could be improved to match the accuracy of Webb’s optics, starting with more laboratory experiments on ground models, refinement of models, and a centralized database with standardized formatting to help astronomers validate their models against Update spectral data and experiments.

“There is so much that could be done if we knew exactly how light and matter interact,” Niraula said. “We know this well enough about Earth’s conditions, but as we move into different types of atmospheres things change, and that’s a lot of data of increasing quality that we risk misinterpreting.”

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