At the telescope, we measure the change in the wavelength (color) of light coming from a star over the course of days, months, and years. This changing wavelength is the Doppler shift of the light, resulting from the star orbiting a common center of mass with a companion planet. For example, Jupiter's gravitational pull causes the Sun to wobble around in a circle with a velocity of 12 meters per second.

Planet Hunting Technique:

  • The Physics Equations of Orbital Motion

  • A Spectrometer in Action
  • The High-Resolution Spectrometer at the Keck Telescope
  • Our Doppler technique paper:
  • Otto Struve's 1952 Proposal for Detecting Planets
  • Other Planet-detection Techniques
  • Shockwave animations from the "How Stuff Works" web site