= Exoplanet secondary eclipse
An <exoplanet secondary eclipse> occurs when a <planet> passes behind its host <star>. Immediately outside the event the detector receives light from both bodies; during complete occultation it receives only stellar light. Their difference isolates planetary light, consisting of reflected stellar <radiation>, planetary <thermal radiation>, or both. Its fraction of the combined out-of-eclipse light is the eclipse depth.
Measuring that depth across <wavelengths> gives <occultation spectroscopy> of the visible dayside. The <thermal eclipse depth> connects a simple <blackbody> model to the <radius> ratio and <brightness temperature>. At visible <wavelengths>, reflected light can instead constrain <geometric albedo>. Changes in the host <star> or detector response must be modelled because the planetary signal is a small difference between two much brighter measurements.
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