Doppler spectroscopy, also known as radial velocity or Doppler shift spectroscopy, is a method used in astronomy to detect and measure the movement of celestial bodies, primarily stars and exoplanets. This technique relies on the Doppler effect, which causes the wavelength of light emitted by an object to shift depending on its relative motion. By observing these shifts in the spectrum of light emitted by a star or planet, astronomers can infer the presence of orbiting planets or other companion objects. Doppler spectroscopy has been widely used to discover and characterize exoplanets and their orbits, providing valuable insights into the diversity and distribution of planetary systems in our galaxy.