= Exoplanet transmission spectrum
= Exoplanet transmission spectra
{synonym}
An <exoplanet transmission spectrum> is the measured <exoplanet transit depth> as a function of <wavelength>. Light from the <star> passing through the limb of an <exoplanet atmosphere> is absorbed or scattered differently in different spectral bands. At a strongly absorbing <wavelength>, a ray becomes opaque farther from the centre, making the effective planetary <radius> larger.
The <annulus model for transmission spectroscopy> estimates the extra blocked <area>, while the <slant optical depth of an isothermal atmosphere> explains why this method can detect tenuous gas. Molecular-band amplitudes depend on the <atmospheric scale height>, abundances, and <exoplanet cloud deck>. <Stellar contamination of a transmission spectrum> and <reference-pressure degeneracy in transmission spectroscopy> limit how directly this observable can be translated into a unique composition.
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