This is a high school lesson plan on the topic of periodic motion. Students analyze data obtained from high-energy satellites of various binary stars orbital periods, then construct their own pendulum in a hands-on lab. The lesson provides multiple animated instructions to help students through each step of the process. It was developed by the Imagine the Universe project through NASA’s Goddard Space Flight Center. This item is part of a larger collection of K-12 resources. See Related items on this page for links to other lessons/tutorials.