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Which atmospheric gases have been identified on close-in giant extrasolar planets?
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Extrasolar planet
Artist's conception of the extrasolar planet HD 209458b, some 150 light-years from Earth.
Spectroscopic studies of close-in giant extrasolar planetsāoften referred to as "hot Jupiters"āhave successfully identified several gases in their upper atmospheres. By analyzing variations in the depth of a planet's transit across its host star at different wavelengths, astronomers have detected the presence of the following atmospheric gases:
These observations are made possible through transit photometry and spectroscopic analysis, which allow researchers to characterize the composition of these distant worlds despite the extreme difficulty of detecting them directly due to the overwhelming brightness of their host stars.1