Accurate Doppler Accelerometry of Stars. Dr. McMillan will continue measuring changes in the radial velocities of solar-type stars to search for gravitational perturbations by planets. The data now span 5 years, a time scale comparable to some planetary orbital periods. Over 2300 observations of 16 stars similar to the Sun have been accumulated. These observations show that the instrument is stable enough to reveal the kinematic effects of Jupiter-size planets. The velocities of some of the target stars appear to be changing slowly. As the length of the data series increases, new observations with unaltered instrumentation become more and more valuable because they increase the sensitivity and frequency resolution in the series' periodograms. Longer term observations are necessary to see whether the apparent variations in velocity are periodic.
