Timing pulsars: An exercise in statistical analysis and the scientific process
Keywords:pulsars, error analysis, standard deviation, standard error, confidence intervals, period
A lab activity for teaching students the fundamentals of statistical analysis by timing pulsar periods is described. The electromagnetic pulses of pulsars have been mapped to sound and uploaded on social media channels, allowing students to “listen” to the beat of the pulsar. Because these beats are extraordinarily precise, they can serve as cyclic events of known time duration. The three-step process described in this article first requires that students select a timing method of low random error found by comparing standard deviations between two suggested methods. In the second step, students reduce systematic error by calibrating their optimal method using a pulsar of known time duration. Finally, students time an unknown pulsar (the mystery pulsar) using the optimal method chosen in Step 1 and calibrating out the bias found in Step 2. By expressing their results in terms of confidence intervals, they use a professional pulsar database to identify the mystery pulsar. Because students are not informed of the identity of the pulsar until after they turn in their lab reports, they are compelled to perform the measurements as carefully and objectively as possible. This activity provides a perfect vehicle for astronomy labs at the beginning of a semester — including online instruction — because it requires no prior instruction in astronomy and no equipment other than the stopwatch on a cell phone and internet connection. Furthermore, this activity offers an introduction to pulsars and such physics topics as magnetism and the conservation of angular momentum.