Suppose you are using the Doppler technique to discover planets around another star.

What type of data will you use and what will you do with the data to make a firm discovery?

Radial Velocity Method

Explanation:

Doppler Shift (also known as the radial velocity method) : This method relies on the fact that the planet and star are both orbiting a shared center of mass. If the orbit is edge-on, the star will move towards us and then away from us in its tiny orbit. When an object is moving towards us, the light we detect is blue-shifted (we see the light at shorter wavelengths than normal) and when an object is moving away from us, the light we detect is red-shifted (we see the light at longer wavelengths than normal). The Doppler shift for light is very similar to the Doppler shift for sound which you have probably witnessed if you've ever stood on the side of the road when an ambulance passed by. The ambulance's sirens sound different when they are approaching than when they are receding because the sound waves are compressed and then stretched. These changes in the star's spectrum (a plot of brightness coming from the star versus wavelength) due to the Doppler shift can be detected. This method has detected a good portion of all discovered extrasolar planets.