Barycentric motion of the host star for a selection of representative multiple exoplanet systems. Main plots (central two columns) show the orbit over the indicated time interval in a reference frame with the system barycentre at the origin, with abscissae and ordinates in AU (the solar diameter is R_⊙ = 6.96 × 10⁸ m, or 0.00465 AU). To the outer side of each orbital sequence, plots show the orbital angular momentum, L_z (upper), and dL_z/dt (lower) for the same time interval, in the units as given in Table 1. For the systems shown, star masses lie in the range 0.85−1.15   M_⊙ except for BD +20 2457 which is  ~2.8 M_⊙. Orbital parameters were taken as follows: the Sun: Seidelmann (2005); BD +20 2457: Niedzielski et al. (2009); HD 168443: Wright et al. (2009); μ Ara: Pepe et al. (2007); 61 Vir: Vogt et al. (2010); and HD 37124: Vogt et al. (2005).