Doppler Effect: Detecting Exoplanets and Star Motion

The Doppler Effect is the change in wavelength of waves when the source moves relative to the observer.
In astronomy, it shifts starlight toward red when moving away and blue when moving closer.
This “redshift” and “blueshift” helps measure how fast stars and galaxies move.
The technique reveals exoplanets by detecting tiny wobbles in their host stars.
These wobbles occur because planets tug gravitationally on their stars as they orbit.
The first exoplanet around a Sun-like star, 51 Pegasi b (1995), was found using the Doppler method.
Doppler measurements can determine an exoplanet’s mass and orbital period.
It’s also used to study binary star systems and orbiting black holes.
The effect was first described in 1842 by Austrian physicist Christian Doppler.
Today, ultra-precise spectrographs detect star motions as small as 1 meter per second—walking speed!