= Methods of detecting exoplanets
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<Methods of detecting exoplanets> infer or resolve an <exoplanet> through its effects on the host <star>'s light or through its own light. The observable determines what can be learned:
* <Doppler spectroscopy> measures changes in a <star>'s line-of-sight <velocity> from its <spectral lines>, constraining a companion's <mass>, <orbital period>, and <orbital eccentricity>, with an <orbital inclination> ambiguity.
* <Exoplanet transit photometry> measures a repeating dip in the <star>'s <observed radiative flux>, constraining the <exoplanet>'s <radius> relative to the <star> and its <orbital period>. It requires a suitably aligned <orbit>.
* <Astrometry> measures a <star>'s changing position on the sky from <stellar reflex motion>; with adequate orbital coverage it can constrain <orbital inclination> and the companion's true <mass>.
* <Gravitational microlensing> detects a companion's perturbation of the temporary brightening of a background <star>. Such alignments are usually not repeatable, and additional information is needed to turn fitted ratios into absolute <masses> and separations.
* <Exoplanet direct imaging> spatially separates an <exoplanet>'s light from its host <star>'s light, enabling studies of an <exoplanet atmosphere> and, over time, its <orbit>.
An <exoplanet secondary eclipse> measures the loss of the <exoplanet>'s light when it passes behind its <star>, complementing <exoplanet transit photometry>. A detection method also selects which systems are easiest to find: deeper <exoplanet transits> favour larger <radius> ratios, and larger <stellar radial-velocity semi-amplitudes> favour more massive companions, shorter <orbital periods>, and larger $\sin i$. These preferences must be accounted for when inferring the underlying <exoplanet> population.
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