Which method detects exoplanets through a star's wobble toward and away from Earth?

Which method detects exoplanets through a star's wobble toward and away from Earth? The answer is radial velocity.

A planet and its star orbit their shared center of mass, so the star moves slightly toward and away from an observer. Astronomers detect this motion by measuring Doppler shifts in the star's spectral lines: motion toward Earth produces a blueshift, while motion away produces a redshift.

The technique is also called Doppler spectroscopy or the wobble method. It does not photograph the planet directly, unlike direct imaging, and it does not measure a temporary brightening caused by gravitational lensing, as microlensing does. The transit method instead detects a planet crossing the face of its star and causing a small dip in brightness.

Radial-velocity observations can estimate a planet's minimum mass and orbital period. Because the method measures only motion along the line of sight, the planet's true mass usually requires additional information about the orbit's inclination. Otto Struve proposed the approach in 1952; 51 Pegasi b became the first planet confirmed around a Sun-like star using it in 1995.