: Pulsars, the quickly rotating dense remnants of supernovas, are commonly found in orbit with other stars. Provided the orbit is not face-on, the pulsar's orbital motion creates a regular variation in the frequency of the radio waves emitted by the pulsar as the star moves toward and away from Earth. A pulsar discovered in 2007 by Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Virginia, and his colleagues displayed an unusual nonregular pattern of variations. After a year and a half of observations, the team members believe they have found the first example of a three-star system in which one of the stars is a pulsar. Based on the data, the system consists of a 1.4 solar mass pulsar that orbits a 0.2 solar mass white dwarf every 1.6 days and a 0.41 solar mass white dwarf that orbits the other two stars every 327 days. The arrangement may allow for the most precise test yet of the equivalence of gravitational and inertial mass predicted by general relativity.