Methods of detecting exoplanets
ID: methods-of-detecting-exoplanets
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 . These preferences must be accounted for when inferring the underlying exoplanet population.
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