... star is watched for a very long time, the net effect of this gravitational pull is a slight wobble in the stars position. The amplitude of the "wobble" depends on the orbital distance of the planet (ap) and the mass of the two bodies (m* and mp), as shown in the equation below: Radial Velocity = 30mpsini 0.5apm* There are two basic methods of seeing this gravitational effect: * Astrometric * Radial velocity detection Astrometric detection: as a planet orbits a star, it exerts a gravitational pull on the star. If a periodic change in position is seen, this can indicate an orbiting body, and analysis of these measurements can give information on the nature of this body. Radial Velocity Detection: as the planet "tugs" at its star, the change in the stars position will cause a Doppler shift in the light from the star. As the star is pulled away slightly, the observed wavelength is ...

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