Orbital motions in the triple system. The orbits are drawn to scale, showing the actual motions of the two stars (red and yellow) and the pulsar (white). The first ten seconds are played relatively slowly, showing the motion around the inner orbit, then we speed up to see the motion around the outer orbit. For a sense of the time scale, an "MJD" is a modified Julian day, so a single day long. The larger left panel shows all three bodies, with trails marking the motion of the outer companion and the center of mass of the inner system. The inset in the top right zooms in on the inner system, showing the pulsar and the companion, with trails marking their orbits. The dots that appear on the orbits mark moments when we have observations of the system, color-coded by telescope; it should be clear that we have quite thorough coverage of both orbits. Each measurement tells us the distance to the pulsar to within a kilometer, so that we can measure the tiny deviations of these orbits from perfect Keplerian ellipses, allowing us to reconstruct the orbits.
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