Astronomy
Thermal Emission from Exoplanets and Atmospheric Characterization
Quick fact
During a secondary eclipse, when an exoplanet passes behind its star, astronomers measure the drop in infrared light to isolate the planet's own thermal emission. This allows them to reconstruct the planet's dayside temperature and even identify molecules like water vapor or carbon monoxide in its atmosphere.
Why this is interesting
Most exoplanets are too far and too faint to photograph, yet we can still know the temperature and some of the gases in their atmospheres. How? By measuring the tiny infrared 'glow' that the planet emits, together with a clever trick called a secondary eclipse.