The star 51 Pegasi shows a regular variation in redshift, indicating that it is orbiting around a common barycentre. This indicates the possibility that it is a single-line spectroscopic binary or that it has a planet of significant mass orbiting it. Fit a curve to the given data as a first step in determining which of these possibilities is the case.

For more information on how to do this problem, and for tables of relevant data, see www.canismajor.ca.